School of Aeronautics and Astronautics Purdue … of Aeronautics and Astronautics Purdue University Research Report 1997-98 ... We are here to prepare men and women to be leaders in

School of Aeronautics andAstronautics

Purdue University

Research Report1997-98

Academic Year

1282 Grissom HallWest Lafayette, Indiana 47907-1282

(765) 494-5117http://aae.www.ecn.purdue.edu

School of Aeronautics and Astronautics 1997-1998 Research Report 1

TABLE OF CONTENTS

OUR MISSION......................................................................................................................... 2

HIGHLIGHTS.......................................................................................................................... 2

ENROLLMENT AND DEGREES AWARDED ..................................................................... 2

INDUSTRY HIGHLIGHTS..................................................................................................... 2

PUBLICATIONS...................................................................................................................... 3

CO-OP PROGRAM ................................................................................................................. 3

FACULTY FOR THE 1997-98 ACADEMIC YEAR .............................................................. 4

OVERVIEW OF RESEARCH AREAS AND FACILITIES .................................................. 6

FACULTY SUMMARY ......................................................................................................... 10

AERODYNAMICS................................................................................................................. 11

DYNAMICS & CONTROL ................................................................................................... 31

PROPULSION........................................................................................................................ 47

STRUCTURES & MATERIALS........................................................................................... 51

ACTIVE RESEARCH PROJECTS....................................................................................... 80

RESEARCH AND OTHER SCHOLARLY ACTIVITIES................................................... 81

GRADUATE THESES ........................................................................................................... 86

COLLOQUIUM SERIES....................................................................................................... 90

HIGHLIGHTS OF FACULTY ACCOMPLISHMENTS..................................................... 93

STUDENT ACHIEVEMENT HIGHLIGHTS ...................................................................... 94

ALUMNI HIGHLIGHTS....................................................................................................... 95

CURRICULUM AND COURSE OFFERINGS .................................................................... 96


OUR MISSION

The School of Aeronautics and Astronautics, established as an independent schoolon July 1, 1945, is committed to be a world-class leader in aerospace engineeringeducation and fundamental and breakthrough research for aerospace vehicles andsystems. We are here to prepare men and women to be leaders in aerospace engineeringby providing exceptional education and research programs for them. Our faculty,students, and staff are dedicated to honest and ethical professional conduct coupled with ateamwork focus.

HIGHLIGHTS

During the fiscal year 1997-98, 40 students earned their Bachelor of Sciencedegree, 19 earned their Master of Science degree, and 14 earned Doctor of Philosophydegrees. The four areas of concentration continue to be Aerodynamics, Dynamics andControl, Propulsion, and Structures and Materials. This year, the U. S. News and WorldReport ranked our graduate program sixth in the nation.

ENROLLMENT AND DEGREES AWARDED

The School had 158 undergraduate students (excluding freshmen) beginning theFall of 1998. Graduate enrollment was 131, with 59 students in the M. S. Program and72 in the Ph.D. program. A summary of degrees awarded is given below for the past fiveyears. Master's and Ph.D. theses published during the 1997-98 academic year aresummarized in the Graduate Theses section.

Degrees AwardedSchool of Aeronautics & Astronautics

Year 93-94 94-95 95-96 96-97 97-98B. S. 96 71 78 48 40M. S. 35 35 36 30 19Ph.D. 10 13 13 17 14

INDUSTRY HIGHLIGHTS

With the support from the Boeing Company and the Intel Corporation, the Schoolwas able to build its new Design/Build/Test Laboratory, which will prepare students forthe integrated teams that industry uses for better design and reduced cycle time. Also, theaddition of the DBT Laboratory will facilitate the reduction of build time and give ourstudents a complete design and manufacturing experience.


Industry membership in the School's long-standing Industrial Affiliates Programincluded: AlliedSignal, The Boeing Company, Hughes Space and CommunicationsCompany, Northrop Grumman Corporation, and Thiokol.

PUBLICATIONS

Listings of books, journal articles, and other printed conference papers and reportspublished in calendar year 1997 are given in the “Faculty Summary” section of thisreport. Only documents which actually appeared in print during 1997 are listed. Notethat 64 journal articles or book chapters, and 127 conference papers or technical reportswere presented or published. In addition to the published technical reports listed, manyother technical progress reports were submitted directly to project sponsors.

CO-OP PROGRAM

During the 1997-98 academic year, 41 students were enrolled in the CooperativeEngineering Program with the 12 companies listed below. This popular program islimited only by the number of industry positions available.

Co-Op CompaniesSchool of Aeronautics and Astronautics

July 1, 1997-June 30, 1998

Company Location Number of A&AECo-op Students

Aerospace Corporation Los Angeles, CA 1Allison Gas Turbine Indianapolis, IN 6Ball Aerospace Boulder, CO 1Delta Airlines Atlanta, GA 1General Electric Cincinnati, OH 2Hughes Space & Communications Los Angeles, CA 1McDonnell Douglas St. Louis, MS 3NASA-Ames-Dryden Edwards, CA 2NASA-Goddard Greenbelt, MD 1NASA-Johnson Space Center Houston, TX 9NASA-Langley Research Center Hampton, VA 5Structural Dynamics Research Center Milford, OH 9


FACULTY FOR THE 1997-98 ACADEMIC YEAR

Aerodynamics G. A. Blaisdell, Associate Professor; Ph.D., Stanford, 1991, computational fluidmechanics, transition and turbulence. S. H. Collicott, Associate Professor; Ph.D., Stanford, 1991, experimental and low-gravity fluid dynamics, optical diagnostics, applied optics.W. A. Gustafson, Professor and Associate Head; Ph.D., Illinois, 1956, hypersonicaerodynamics, spacecraft design.A. S. Lyrintzis, Associate Professor; Ph.D., Cornell, 1988, computationalaeroacoustics, aerodynamics for rotorcraft and jet flows.S. P. Schneider, Associate Professor; Ph.D., Caltech, 1989, experimental fluidmechanics, high-speed laminar-turbulent transition.J. P. Sullivan, Professor and Head; Sc.D., MIT, 1973, experimental aerodynamics,propellers, laser-doppler velocimetry.M. H. Williams, Professor; Ph.D., Princeton, 1975, aerodynamics, computational fluidmechanics.

Dynamics and Control D. Andrisani II, Associate Professor; Ph.D., SUNY at Buffalo, 1979, estimation,control, dynamics.M. J. Corless, Professor; Ph.D., Berkeley, 1984, dynamics, systems, control.A. E. Frazho, Professor; Ph.D., Michigan, 1977, control systems.K. C. Howell, Professor; Ph.D., Stanford, 1983, orbit mechanics, spacecraft dynamics,control; trajectory optimization.J. M. Longuski, Associate Professor, Ph.D., Michigan, 1979, spacecraft dynamics,orbit mechanics, control, orbit decay and reentry.M. A. Rotea, Associate Professor; Ph.D., Minnesota, 1990, robust and nonlinearmultivariable control, modeling and identification.R. E. Skelton, Professor; Ph.D., UCLA, 1976, dynamics of aerospace vehicles, controltheory.

PropulsionS. D. Heister, Associate Professor; Ph.D., UCLA, 1988, rocket propulsion, liquidpropellant injection systems.


Structures & MaterialsW. A. Crossley, Assistant Professor; Ph.D., Arizona State, 1995, optimization,rotorcraft and aircraft design, structure design.J. F. Doyle, Professor; Ph.D., Illinois, 1977, structural dynamics, experimentalmechanics, photomechanics, wave propagation.H. D. Espinosa, Associate Professor; Ph.D., Brown, 1992, micromechanics of ceramicsand composites, experimental and computational mechanics.T. N. Farris, Professor, Ph.D., Northwestern, 1986, tribology, manufacturingprocesses, fatigue and fracture.A. F. Grandt, Jr., Professor; Ph.D., Illinois, 1971, damage-tolerant structures andmaterials, fatigue and fracture, aging aircraft.C. T. Sun, Professor; Ph.D., Northwestern, 1967, composites, fracture and fatigue,structural dynamics.T. A. Weisshaar, Professor; Ph.D., Stanford, 1971, aircraft structural mechanics,aeroelasticity, integrated design.


OVERVIEW OF RESEARCH AREAS AND FACILITIES

Excellent computational facilities are available at Purdue University and includean 142-node Intel Paragon parallel computer, with 32 MB memory per node, which isavailable as a shared resource with unrestricted access. Purdue also owns an 18-nodeIBM SP-2.

With the support of the Boeing Company and the Intel Corporation, the Schoolwas able to build its new Design/Build/Test Laboratory, which will prepare students forthe integrated teams that industry uses for better design and reduced cycle time. Also theaddition of the DBT Laboratory will facilitate the reduction of the build time and give ourstudents a complete design and manufacturing experience.

In addition, many workstations and personal computers are located throughout theSchool of Aeronautics and Astronautics. High performance computing is available usingmultiple IBM RS/6000, Silicon Graphics and Sun Microsystems computers. Clustercomputing, using single and dual Intel Pentium Pro and Pentium II systems, is a recentaddition, complementing the main Sun Microsystems compute servers.

AERODYNAMICS

Aerodynamics research is directed toward a better understanding of thefundamental laws governing the flow of fluids. Research topics of recent interestinclude: numerical methods in aerodynamics; computational fluid mechanics; separatedflow around wings and bodies at high angles of attack; aerodynamics of rotors andpropellers; boundary layers, wakes and jets in V/STOL applications and aerodynamicnoise; hypersonic and chemically reacting flows; experimental measurements using lasersystems; laminar-turbulent transition in high speed boundary layers.

Experimental facilities include four wind tunnels located at the AerospaceSciences Laboratory. The Boeing Wind Tunnel is a large subsonic wind tunnel withtwo test sections -- a closed 4-by-6 foot section with a maximum speed of 250 miles perhour and a long test section adapted for high-lift research. The first test section isequipped with a six-component motorized pitch-and-yaw balance system.Instrumentation includes a two-component laser Doppler velocimeter system and acomputer data acquisition system.

Three smaller low-speed wind tunnels are also located at the ASL. One has an18-inch diameter test section, and the other two have test sections of 12x18 inches. Also,a 2-inch, supersonic, blow-down type wind tunnel that can operate from Mach 1.5 toMach 4 is housed at the ASL. This tunnel’s air supply can be used for an adjacent gasdynamical flow apparatus designed for nozzle-flow studies.

Lastly, a supersonic quiet flow Ludwieg tube with a 4-inch, Mach-4 test sectionis located in the Boeing Compressible-Flow Laboratory, which also houses other


compressible-flow facilities. Both of the supersonic tunnels can be operated in pressure-vacuum mode. A 4-inch shock tube is available for instrumentation work. Several smallsmoke and calibration tunnels, water tables and tow tanks are also available.

DYNAMICS AND CONTROL

All modern aerospace vehicles rely upon an understanding of dynamics andcontrol to improve system performance. Successful system design requires anunderstanding of the interactions of dynamic elements, and the trade-offs between vehicledynamic characteristics, control system properties, and system performance.

Current research is divided into the following areas: aircraft design for improvedhandling qualities, astrodynamics, control and estimation theory, dynamics and control offlexible spacecraft, mission design, modeling and control of aeroelastic aircraft,spacecraft maneuvers and trajectory analysis and optimization.

Certain research projects in the dynamics and control area require advanced andspecialized laboratory facilities. A helicopter experiment is also available for teachingcontrol. The helicopter consists of the fuselage, the main motor (for pitch control), andthe tail motor (for yaw control). The objective is to model, identify, and control the pitchand yaw axis of the helicopter. The helicopter is connected to a MAC IIsi for the purposeof driving the main and tail motors and measuring the pitch and yaw motion. The FlightDynamics and Control Laboratory contains several analog computers with somenonlinear components, X-Y plotters, oscilloscopes, and signal generation devices forstudying dynamic systems and evaluating feedback control laws. The Flight SimulationLaboratory has fixed-base, digital flight simulation capabilities with force-sensitivemanipulators and CRT display for pilot-in-the-loop experiments. The simulations arecontrolled by a 16-bit microprocessor with a 40-mb hard disk for storing experimentaldata. Here, pilot/vehicle performance, workload, and vehicle dynamics are studied. Aninstrumented Remotely Piloted Vehicle, currently under development, represents aunique research facility upon which to perform many experiments in vehicle dynamicsand control. Data communication with a computer based ground station is provided by aseven channel telemetry downlink. The Space Systems Control Laboratory is locatedwithin the Institute of Interdisciplinary Engineering Studies, and involves faculty fromthe School of Aeronautics and Astronautics, School of Electrical Engineering, School ofMechanical Engineering, the Department of Computer Science, and the Department ofMathematics. The Space Systems Control Laboratory is a national resource for rapidanalysis and design of spacecraft control systems.


PROPULSION

There are two broad categories in propulsion research: (1) devices that need air toproduce thrust, and (2) devices that do not need air to produce thrust. The first categoryincludes piston engines, turbojet engines, turbofan/propeller engines, and scramjet andramjet engines. The second category includes various rocket engines. In the past severalyears, the emphasis in the School of Aeronautics and Astronautics has been on both ofthese types of propulsion systems.

The Rocket Propulsion Laboratory contains unique facilities for basic researchon rocket propulsion. Major equipment includes a hybrid rocket engine test stand whichhas recently been constructed to investigate combustion and performance of theseengines. A large, high pressure air supply is available for air-augmented rocket andramjet combustion studies. A minicomputer is available for data acquisition/reduction.These facilities are housed in the Thermal Sciences and Propulsion Center.

In addition, propulsion research facilities are also housed in the AerospaceSciences Laboratory. Facilities have been developed to investigate combustor burn-through in turbojet engines using laser sheet flow visualization, thermal paintfluorescence, and pressure paint fluorescence of a jet impinging at various angles to aplate.

STRUCTURES AND MATERIALS

Structures and materials research includes work in composite materials,computational structural mechanics, damage tolerance analysis, experimental structuralanalysis, structural mechanics and aeroelasticity, tribology, manufacturing, wavepropagation, smart materials and structures, and optimal design methods.

The McDonnell Douglas Composite Materials Laboratory contains equipmentand facilities for general material testing and for fabrication of composite laminates. Anautoclave specially designed for curing epoxy-matrix composites is available for laminatefabrication. A hot press is used for forming thermoplastic composites, and an EnTecfilament winding machine is available for making cylindrical composite structures. Awater jet cutting machine is used for specimen preparation. Four complete MTS materialand fatigue testing machines (55 kip, 22 kip, 11 kip, and 1 kip capacity) and associatedequipment are used to perform ultimate strength, stiffness, and fatigue tests on variouscomposite materials. Nondestructive inspection equipment includes an x-ray machineand an ultrasonic C-scan system. Additional facilities for preparing laminatedcomposites, impact testing, and creep testing are available.

The Dynamic Inelasticity Laboratory consists of a 3" gas gun and opticalinstrumentation for wave propagation studies. The facility has been designed for theinvestigation of damage and failure mechanisms in advanced materials. Soft recovery of


the impacted targets, which is accomplished by specially designed target fixtures andenergy dissipation mechanisms, allows the identification of stress-induced microdefectsand phase changes by means of microscopy studies. Optical instrumentation, togetherwith a 1 Watt single mode argon ion laser, and two four channel oscilloscopes (TektronixDSA 602A, LeCroy 9384L) with maximum sample rate up to 4 Gs/sec, 1Ghz bandwidth,and a 8 MB memory allow the use of multi-point laser interferometry. Theinterferometry used for interface and free surface velocity measurements in wavepropagation experiments includes: Normal Velocity Interferometer (NVI), TransverseDisplacement Interferometer (TDI), Variable Sensitivity Displacement Interferometer(VSDI), and fiber optic Velocity Interferometer for any Reflecting Surface (VISAR). Inaddition to the laser interferometric technique, in-material stress measurements areperformed using piezoresistance gauges. High temperature dynamic testing is performedwith a Lepel LSP 12-25-30, 25 KW heat induction system and accessories for heatingmetallic and nonmetallic samples up to 1400°C. The lab computational facility consistsof three Sun Workstations Sparc 20 and one Sparc 2 served by an Ultra Sparc 2 with two167 MHz processors and 4GB+2GB hard disks, Hewlett Packard laser printers, and a PCwith 150 MHz Pentium microprocessor, 1.6GB hard disk, 6x CD-ROM, 3.5 floppy drive,28kb modem/fax.

The Fatigue and Fracture Laboratory is well-equipped to determinemechanical properties of structural materials. Two computer-controlled electro-hydraulictest machines (11 kip and 22 kip capacity) and associated equipment are available tomeasure fracture loads and to study fatigue crack formation and propagation in testspecimens subjected to simulated aircraft or spacecraft load histories. Facilities are alsoavailable to artificially corrode specimens in connection with corrosion and/orcorrosion/fatigue related research.

The Structural Dynamics Laboratory has the latest equipment for recordingultra-dynamic events. Major equipment includes Norland and Nicolet digital recorders, aone-million-frame-per-second dynamic camera, impact gun, and various computerperipherals for data acquisition. The primary research interest is in the impact ofstructures and the analysis of consequent stress waves.

The Tribology and Materials Processing Laboratory contains tribologicalinstrumentation as well as up-to-date machines for manufacturing processes. Equipmentincludes a 22 kip computer-controlled electro-hydraulic test machine and associatedequipment for fretting fatigue testing, infrared sensors for temperature measurements, afriction apparatus for both low and high speed sliding indentation, a residual stressanalyzer, lapping and polishing equipment, a vibration isolation table, micropositioningstages, rolling contact fatigue testers, Talysurf profilometers, optical microscopes, and ahigh pressure pump used for dynamic fracture experiments. Also, access is available to avariety of machine tools including a precision lathe from Hardinge, a precision highspeed surface grinder, a centerless grinder, and a super finishing machine, as well asassociated piezoelectric force transducers.


SCHOOL OFAERONAUTICS & ASTRONAUTICS

FACULTY SUMMARY


AERODYNAMICS


GREGORY A. BLAISDELL1991

Associate Professor

DegreesB. S., California Institute of Technology, Applied Mathematics, 1980M. S., California Institute of Technology, Applied Mathematics, 1982Ph.D., Stanford University, Mechanical Engineering, 1991

InterestsComputational fluid mechanicsTransition and turbulence

Awards and Major AppointmentsNASA-ASEE Summer Faculty Fellowship, 1995-1996W. A. Gustafson Teaching Award, Fall 1997

Research AreasCurrent research interests involve the study of transitional and turbulent fluid

flows using computational fluid dynamics (CFD) as an investigative tool. Most flows ofengineering interest are turbulent and turbulence has a significant impact on theperformance of engineering systems. The drag on a body is generally much greater if theboundary layer is turbulent. Turbulence also increases heat transfer between a fluid and asurface. In addition, turbulent mixing is important to combustion.

The physics of basic turbulent flows are studied using direct numericalsimulations (DNS) and large-eddy simulations (LES). With LES the motion of thelargest eddies are solved for directly while the effects of the unresolved small scaleeddies are modeled. In contrast, with DNS all the relevant length scales within theturbulence are resolved and no modeling is needed. The results of the simulations are


used to increase our understanding of turbulence and to test and improve turbulencemodels.

Current research projects are described below. Many of these investigations arebeing carried out using parallel processing computers. Parallel computing and advancednumerical methods is another area of interest.

Direct Numerical Simulation of a Turbulent Axial Vortex (sponsored by PurdueResearch Foundation, IBM SUR Program, Student: Jim H. Qin; Computer Resources:PUCC (IBM SP2, Intel Paragon), PSC (Cray C90))

Axial vortices form in many engineering systems but are of particular importanceto the wake hazard problem for commercial aircraft. The current study uses directnumerical simulation (DNS) to investigate an isolated turbulent axial vortex. The meanflow includes a wake-type axial velocity which causes the flow to be unstable. As theflow develops the wake deficit decreases to the point that the flow becomes stabilized, inagreement with previous simulation results. The Reynolds stress profiles from the DNSare found to compare well qualitatively with those from experiments. At later times thevortex core experiences negative diffusion of axial vorticity so that the vortex windstighter. This is in contrast to the usual case in which turbulence is a diffusive process.An eddy viscosity based on the production of turbulent kinetic energy exhibits negativevalues in the core region. Such behavior is not captured by standard turbulence models.Examination of vortex structures during the period of turbulence growth shows thepresence of helical vortices similar to the linear instability modes. As the flow isstabilized these large scale structures disappear.

Development of Large Eddy Simulation Methodology and Application to aTurbulent Axial Vortex (Sponsored by Purdue Research Foundation; Graduate student:Brijesh Eshpuniyani; Computer resources: PUCC (IBM SP 2))

This research project will consider means of accounting for the effect oftruncation errors in LES. The techniques developed will then be applied to the large eddysimulation of a turbulent axial vortex. This study is a follow-on to the above project withJim Qin using DNS. However, the DNS are limited to low Reynolds numbers - the DNSare at a Reynolds number that is three orders of magnitude lower than that of the wakevortices behind a typical large commercial airliner. Although LES on currently availablecomputers will not be able to achieve full scale Reynolds numbers, it will allow thetrends with increasing Reynolds numbers to be determined. This is important becauseReynolds number is believed to have a significant effect on the development ofturbulence within a vortex.

On the Development of Supersonic Jet Noise Prediction Methodology - (Co-investigator: Anastasios S. Lyrintzis (Purdue, AAE), sponsored by the NASA LewisResearch Center, Graduate Student: Evangelos K. Koutsavdis; Computer Resources:PUCC (IBM SP2))


A new Computational Aeroacoustics (CAA) methodology for accurate predictionof supersonic jet noise from first principles will be developed. First, a three-dimensionalLarge Eddy Simulation (LES) code based on the dynamic subgrid scale model will bedeveloped. Then Kirchhoff's method will be employed for the extension ofComputational Fluid Dynamics (CFD) results to the far-field. Kirchhoff's method allowsradiating sound to be evaluated based on quantities on an arbitrary control surface, if thelinear wave equation is assumed outside. The control surface is assumed to include allthe nonlinear flow effects and noise sources. The solution on the control surface will beevaluated using the LES CFD code described above.

Homogeneous Compressible Turbulence (sponsored by ICASE (Summer Visitor1997), Collaborator: Ray Ristorcelli (ICASE/NASA LaRC); Computer Resources:PUCC (Intel Paragon))

Direct numerical simulations of compressible homogeneous turbulence are usedto study the mechanisms of increased dissipation in compressible turbulence. Resultsfrom these simulations have been used to examine compressibility corrections to two-equation and Reynolds stress turbulence models.

Modeling Diesel Engine Injector Flows (Co-investigator: Stephen D. Heister (Purdue,AAE); sponsor: Army Research Office)

This research effort will extend the development of a computational tool capableof resolving unsteady, viscous, cavitating flow fields inside diesel engine injectorpassages. Fully three-dimensional, unsteady calculations will be performed in order toassess the influence of injector design on the internal flow structure. In addition, aturbulence model will be added to the current laminar methodology in order to addresscomplex processes in the wake and wall regions. Ultimately, this model will provide atool with which engine manufacturers can evaluate design changes rapidly, therebyreducing product development times and improving engine efficiency. Moreover, themodel could be useful in correlating internal flow variables with observed emissions data,thereby providing an important link/methodology to reduce emissions through prudentinjector design.

PublicationsRistorcelli, J. R., and Blaisdell, G. A., "Consistent Initial Conditions for the DNS ofCompressible Turbulence," Physics of Fluids, Vol. 9, pp. 4-6, Jan. 1997.

Hamba, F., and Blaisdell, G. A., "Modeling of Inhomogeneous Compressible TurbulenceUsing a Two-Scale Statistical Theory," Physics of Fluids, Vol. 9, pp. 2749-2768, Sept.1997.


Conference Proceedings, Presentations and Invited LecturesSpyropoulos, E. T., and Blaisdell, G. A., "Large Eddy Simulation of a Spatially EvolvingCompressible Layer Flow," AIAA Paper 97-0429, presented at the 35th AIAA AerospaceSciences Meeting, Reno, NV, (11 pages), Jan. 1997.

Blaisdell, G. A., "Direct Numerical Simulation of a Turbulent Axial Vortex," invitedlecture given to the Department of Theoretical and Applied Mechanics, University ofIllinois at Urbana-Champaign, IL, Feb. 27, 1997.

Blaisdell, G. A., "Commutation of Discrete Filters and Differential Operators for LargeEddy Simulation," Advances in DNS/LES, Proceedings of the 1st AFOSR InternationalConference on DNS/LES, Ruston, LA, pp. 333-340, Aug. 4-8, 1997.

Blaisdell, G. A., "A Review of Benchmark Flow for Large Eddy Simulation," final reportfor the 1997 AFOSR Summer Faculty Program, (18 pages), Aug. 1997.

Ristorcelli, J. R., and Blaisdell, G. A., "Validation of a Pseudo-Sound Theory for thePressure-Dilation in DNS of Compressible Turbulence," Proceedings of the 11th

Turbulent Shear Flow Symposium, Grenoble, France, (9 pages), Sept. 8-11, 1997.


STEVEN H. COLLICOTT1991

Associate Professor

DegreesB. S., University of Michigan, Aerospace Engineering, 1983, magna cum laudeM. S., Stanford University, Aeronautics & Astronautics, 1984Ph.D., Stanford University, Aeronautics & Astronautics, 1991

InterestsExperimental fluid mechanicsLow-gravity fluid dynamicsOptical diagnosticsApplied optics

Awards and Major AppointmentsPresented the American Institute of Aeronautics and Astronautics “SpecialService Citation,” March 1997

Research AreasFour topics are being researched: high-bypass turbofan duct-strut flow, cavitation

in spray orifices, low-gravity fluid dynamics, and optical methods for studyinghypersonic boundary layer transition.

A source of total pressure loss and non-uniform back pressure on the fan inmodern and proposed high bypass ratio turbofan engines is the strut-endwall flow in thebypass duct. NASA-funded experiments, coordinated with advanced concepts research atPratt & Whitney, explore the flow structure at Reynolds numbers typical of full-scale


cruise conditions. The experiment is designed to also provide valuable checkpoints forthe integrated design codes being developed by Pratt & Whitney.

Spraying of a liquid is a common commercial operation, yet little attention hasbeen paid to the flow inside the spray orifice. Particularly in diesel fuel injectors, small-scale non-equilibrium cavitation exists, the behavior of which can not presently bepredicted to any useful extent. This research, funded by the NSF-Career Award, probesthe internal flow with specialized optics to uncover the physics of cavitation andturbulence in these flows. Coordination with Professor Heister's simulations with apseudo-density model for non-equilibrium cavitating flows is crucial to the value of theseexperiments.

Design of fuel tanks to control sloshing liquids during weightless space flightrequires incorporation of nonlinear contact-line dynamics into numerical models. Eventhe determination of equilibrium interface topology requires considerable numerical workin many situations. Validation and application of an existing model for determiningequilibrium interface topologies in main liquid helium tank of the Gravity Probe-Bspacecraft has been performed for Lockheed and the GP-B project. Incorporation ofphysically important stick-slip contact line motion as non-linear boundary conditions in aBoundary Element Method (BEM) code for low-g large-amplitude fluid slosh predictionis being pursued with Professor Heister.

Hypersonic boundary layer transition is a critical event on high speed flightvehicles, including the Space Shuttle during re-entry. Professor Schneider's experimentsinvolve an optical perturber and optical diagnostics, both under the responsibility ofProfessor Collicott. The perturber has been developed and is in regular use. High-sensitivity, high bandwidth Laser Differential Interferometry is being applied to detectand measure instability waves in millimeter and thinner boundary layers in flows atspeeds in excess of one-half of a kilometer per second.

Conference Proceedings, Presentations and Invited LecturesCollicott, S. H., "Experiments in Small-Scale Cavitation in Atomizing Orifice Flows,"52nd Purdue Industrial Waste Conference, W. Lafayette, IN, (13 pages), May 6, 1997.

Henry, M., Collicott, S. H., and Heister, S. D., "Internal Structure of Cavitating SlotFlow," Institute for Atomization and Sprays-Americas, Ottawa, Ontario, (5 pages), May20, 1997.

Collicott, S. H., Sullivan, J. P., Campbell, B., Krautheim, M. S., and Miller, K. A.,"Experiments in High Reynolds Number Duct-Strut Flow," AIAA/ASME/SAE/ASEEJoint Propulsion Conference, Seattle, WA, (11 pages), July 1997.

Krautheim, S., Miller, K. A., Campbell, B., Collicott, S. H., and Sullivan, J. P., "HighReynolds Number Experiments on Bypass Duct and Strut Flows," presented at the 33rd

AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Seattle, WA, July 6-9, 1997.


W. A. GUSTAFSON1960

Professor and Associate Head

DegreesB. S., University of Illinois, Aeronautical Engineering, 1950M. S., University of Illinois, Aeronautical Engineering, 1954Ph.D., University of Illinois, Aeronautical Engineering, 1956

InterestsHypersonic AerodynamicsSpacecraft design

Current Academic ActivitiesProfessor Gustafson has served as the School's Undergraduate Counselor for all

aeronautical and astronautical students since 1981. He advises freshman studentsentering the School of Aeronautics and Astronautics. He also heads of our Co-opProgram, and serves as the Schedule Deputy for our School.

TeachingCourses taught during the past five years:

A&AE 333 Fluid MechanicsA&AE 334 AerodynamicsA&AE 451 Design I (Spacecraft)A&AE 519 Satellite Aerodynamics and Planetary Entry


ANASTASIOS S. LYRINTZIS1994

Associate Professor

DegreesDiploma, National Technical University, Athens Greece, Mechanical

Engineering, 1981M.S., Cornell University, Aerospace Engineering, 1985Ph.D., Cornell University, Aerospace Engineering, 1988

InterestsComputational AeroacousticsAerodynamics for rotorcraft and jet flows

Awards and Major AppointmentsAHS (American Helicopter Society), Acoustics CommitteeAIAA Aeroacoustics, Technical Committee; Awards Subcommittee (Chairman 96-97)ASME: coordinating group for CFDAssociate Fellow AIAA

Research Areasi) Jet Aeroacoustics - Kirchhoff's Method: The success NASA's efforts to develop aHigh-Speed Civil Transport (HSCT) depends on the substantial reduction of jet exhaustnoise. The important features of supersonic jet noise have been studied in the past byvarious investigators. A new approach (i.e. Kirchhoff's method) for shock generatednoise and jet aeroacoustics has been being investigated. The method is being extendedfor including sound sources outside the computational domain as well as refractioncorrections.


ii) Transonic Helicopter Impulsive Noise: In the recent years, the increasing use ofhelicopters has drawn attention to the noise that they generate. Among the several typesof helicopter noise, impulsive noise (i.e. Blade Vortex-Interactions (BVI) and High-Speed Impulsive (HSI)) is the most important. Our current research focuses in theformulation of a prediction model for impulsive noise for hovering and advancing rotorsusing the Kirchhoff technique for the far-field. The method is currently being extendedto supersonically moving sources for HSI noise. Noise reduction techniques are alsoinvestigated.

iii) Efficient Transonic Flow Calculations: With the advent of parallel computers,development of efficient parallel CFD algorithms is needed. An efficient algorithm toparallelize the popular LU-SGS (Lower Upper -Symmetric Gauss Seidel) implicitoperator for unsteady Euler equations has been developed. The algorithm was applied onthe rotorcraft aerodynamics code TURNS (Transonic Unsteady Rotor Navier-Stokes), onthe parallel IBM SP-2 machine. The method is currently being extended to NavierStokes equations, as well as overset grid methodologies (e.g. OVERFLOW code).

An alternative approach for transonic flow equations is to use a Newtontechnique. For each Newton step an efficient conjugate gradient-like iterative method(i.e. GMRES, s-step Orthomin) with proper preconditioning is used. The parallelefficiency for the above method for a test 2D problem was found to be very promising.We are currently investigating application of this method for 3-D unsteady Navier Stokescodes used in the prediction of helicopter aerodynamics.

Sponsored Research Summaries

An Extended Kirchhoff Method for Rotorcraft Impulsive Noise; Sponsor: ARO;Students: E. K. Koutsavdis, A. R. Pilon

Kirchhoff's method has been employed for the extension of Computational FluidDynamics (CFD) results to the far-field. Kirchhoff's method allows radiating sound to beevaluated based on quantities evaluated on an arbitrary control surface, if the linearhomogeneous wave equation is assumed outside the control surface. Thus, the controlsurface is assumed to include all the nonlinear flow effects and noise sources.Kirchhoff's method will be enhanced to include nonlinear quadrupole effects outside thecontrol surface. The control surface can not be very far away from the blade because ofthe diffusion and dispersion errors of the CFD solution due to grid stretching. Thus somenonlinearities may prevail outside the Kirchhoff surface. Since the current estimate of thenonlinear sources outside the control surface is zero, it is feasible that a better estimate ofthem can be made, at very little additional computational cost, and possibly significantimprovement in the fidelity of the radiated noise prediction. Thus, an extended Kirchhoffmethod for rotorcraft aeroacoustics that will include nonlinear effects outside the controlsurface will be developed and validated.


A Study of Rotorcraft Blade-Tip Shape Noise Characteristics; Sponsor: NASALangley; Students: J. R. Jameson, E. K. Koutsavdis

Kirchhoff's method has been employed for the extension of Computational FluidDynamics (CFD) results to the far-field. Kirchhoff's method allows radiating sound to beevaluated based on quantities evaluated on an arbitrary control surface, if the linearhomogeneous wave equation is assumed outside the control surface. Thus, the controlsurface is assumed to include all the nonlinear flow effects and noise sources. Thismethodology has been implemented recently in the NASA Langley TRAC (TiltRotorAeroacoustic Codes) system. The method has been used for rotorcraft high-speedimpulsive (HSI) and Blade-Vortex Interaction (BVI) noise prediction with very goodresults. Blade tip design is a very important noise parameter because noise signals arevery sensitive to tip shapes. The aerodynamic behavior of various tip shapes has beenstudied previously at NASA Langley. We propose here the investigation of the noisecharacteristics of blade tip shapes. We expect to characterize several blade tip shapedesigns and offer ideas for possible noise reduction.

The Use of Kirchhoff's Method in Jet Noise Calculations; Sponsor: NASA Langley;Student: A. Pilon

Research in the development of an improved Kirchhoff method is described. TheKirchhoff method is a means of evaluating radiating sound from flow acoustic quantitieson a computational surface. The linear, homogeneous wave equation is assumed to bevalid in the propagation region, outside this surface (the Kirchhoff surface). The surfacequantities are generally obtained from a computational fluid dynamics (CFD) calculationof the acoustic near--field. This work outlines the development of a Kirchhoff methodfor use when the linear, homogeneous wave equation is not valid in a portion of theregion outside of the Kirchhoff surface. The improved method is derived through the useof a porous--surface formulation of the Ffowcs Williams--Hawkings equation. Thismodified integral solution allows the Kirchhoff methodology to be employed in problemswith large, non--compact source regions that extend beyond the limits of the CFDcalculation. Test calculations are shown to validate the method for use in jetaeroacoustics studies. However, the method is presented in a manner to make it easilyapplicable in cases where Kirchhoff methods have been used in the past. The method ofcomputational aeroacoustics was also modified to account for the refraction caused bynon--uniform mean flows in jet noise calculations. The corrections presented are basedon simplified geometric acoustics principles. An axisymmetric, parallel shear flow isassumed for the jet mean flow which causes the refraction. The corrections are shown toqualitatively approximate the “zone of silence” observed near the axis in jet acousticsexperiments.

On the Development of Supersonic Jet Noise Prediction Methodology; Collaborator:G. A. Blaisdell (Purdue, AAE); Student: E. K. Koutsavdis; Sponsor: NASA Lewis


A new Computational Aeroacoustics (CAA) methodology for accurate predictionof supersonic jet noise from first principles will be developed. First, a three-dimensionalLarge Eddy Simulation (LES) code based on the dynamic subgrid scale model will bedeveloped. Then Kirchhoff's method will be employed for the extension ofComputational Fluid Dynamics (CFD) results to the far-field. Kirchhoff's method allowsradiating sound to be evaluated based on quantities on an arbitrary control surface, if thelinear wave equation is assumed outside. The control surface is assumed to include allthe nonlinear flow effects and noise sources. The solution on the control surface will beevaluated using the LES CFD code described above. Kirchhoff's method will beenhanced to avoid evaluation of normal derivatives and include nonlinear effects as wellas refraction effects outside the Kirchhoff surface.

PublicationsLyrintzis, A. S., and Xue, Y., "Versatile Kirchhoff Code for Aeroacoustic Predictions,"AIAA Journal, Vol. 35, No. 1, pp. 198-200, Jan. 1997.

Lyrintzis, A. S., Koutsavdis, E. K., and Strawn, R. C., "A Comparison of ComputationalAeroacoustic Prediction Methods," American Helicopter Society Journal, Vol. 42, No. 1,pp. 54-57, Jan. 1997.

Brentner, K. S., Lyrintzis, A. S., and Koutsavdis, E. K., "A Comparison of ComputationalAeroacoustic Prediction Methods for Transonic Rotor Noise," AIAA Journal of Aircraft,Vol. 34, No. 4, pp. 531-538, July-Aug. 1997.

Liu, G., Lyrintzis, A. S., and Michalopoulos, P. G., "Numerical Simulation of FreewayTraffic Flow," ASCE Journal of Transportation Engineering, Vol. 123, No. 6, pp. 503-513, Nov.-Dec. 1997.

Conference Proceedings, Presentations Invited LecturesScott, J. N., Pilon, A. R., Lyrintzis, A. S., and Rozmajzl, T., "A Numerical Investigationof Noise from a Rectangular Jet," AIAA paper No. 97-0285, presented at the 35th

Aerospace Sciences Meeting, Reno, NV, Jan. 1997.

Pilon, A. R., and Lyrintzis, A. S., "Integral Methods for Computational Aeroacoustics,"AIAA paper No. 97-0020, presented at the 35th Aerospace Sciences Meeting, Reno, NV,Jan. 1997.

Shih, S. H., Hixon, D. R., Mankbadi, R. R., Pilon, A. R., and Lyrintzis, A. S., "Evaluationof Far-Field Jet Noise Prediction Methods," AIAA paper No. 97-0282, presented at the35th Aerospace Sciences Meeting, Reno, NV, Jan. 1997.

Koutsavdis, E. K., and Lyrintzis, A. S., "An Investigation of Kirchhoff's Methodologiesfor Computational Aeroacoustics," AIAA paper No. 97-0487, presented at the 35th



Wissink, A. M., Lyrintzis, A. S., and Chronopoulos, A. T., "Parallel Krylov SolversApplied to the Rotorcraft CFD Code TURNS," Proceedings of the 1996 ComputationalAerosciences (CAS) Workshop, NASA Ames Research Center, Aug. 1996, NASAConference Publication CD 20011, pp. 43-48, May 1997.

Pilon, A. R., and Lyrintzis, A. S., "Refraction Corrections for the Kirchhoff Method,"AIAA paper No. 97-1654, presented at the 3rd AIAA/CEAS Aeroacoustics Meeting,Atlanta, GA, May 1997.

Spryopoulos, J. T., Douglas, J., and Lyrintzis, A. S., "A New Scheme for theIncompressible Navier-Stokes Equations Employing Alternating-Direction OperatorSplitting and Domain Decomposition - a Preliminary Report," presented at the AmericanMathematical Society (AMS) Meeting #922 Special Section on Partial DifferentialEquations: Theories, Applications, and Numerical Approaches IV, Wayne State Univ.,Detroit, MI, May 1997.

Wissink, A. M., Lyrintzis, A. S., and Chronopoulos, A. T., "A Parallel Newton-KrylovMethod for Rotorcraft Flowfield Calculations," AIAA Paper No. 97-2049, Proceedings ofthe 13th AIAA Computational Fluid Dynamics Conference, Snowmass, CO, pp. 1060-1070, June 1997.

Lyrintzis, A. S., "The Use of Kirchhoff Method in Computational Aeroacoustics,"Mechanical and Aerospace Engineering Seminar, Univ. of California, Los Angeles, CA,June 1997.

Lyrintzis, A. S., "History and Future Prospects of Vertical Flight," presented lecture atthe Aerospace Teacher's Workshop, Purdue University, W. Lafayette, IN, June 1997.

Lyrintzis, A. S., and Pilon, A. R., "An Extended Kirchhoff Method for RotorcraftImpulsive Noise," presented at the Technical Specialists' Meeting for RotorcraftAcoustics and Aerodynamics, Williamsburg, VA, Oct. 1997.

Lyrintzis, A. S., Jameson, J. R., and Koutsavdis, E. K., "A Study of Rotorcraft Blade-TipShape Noise Characteristics," presented at the Technical Specialists' Meeting forRotorcraft Acoustics and Aerodynamics, Williamsburg, VA, Oct. 1997.

Berezin, C., Pollack, M., Visintainer, J., Lyrintzis, A., and Koutsavdis, E., "Developmentand Practical Application of the Rotating Kirchhoff Method for the Prediction of HIS andBVI Noise," presented at the Technical Specialists' Meeting for Rotorcraft Acoustics andAerodynamics, Williamsburg, VA, Oct. 1997.

Caradonna, F., Kitaplioglu, C., McCluer, M., Baeder, J., Berezin, C., Bridgeman, J.,Curley, C., Epstein, R., Koutsavdis, E., Leishman, G. Lyrintzis, A., Rashier, G., andRule, J., "A Review of Methods for the Prediction of BVI Noise," presented at theTechnical Specialists' Meeting for Rotorcraft Acoustics and Aerodynamics,Williamsburg, VA, Oct. 1997.


STEVEN P. SCHNEIDER1989

Associate Professor

DegreesB.S., California Institute of Technology, Engineering & Applied Science, with

Honors, 1981M. S., California Institute of Technology, Aeronautics, 1984Ph.D., California Institute of Technology, Aeronautics, 1989

InterestsExperimental fluid mechanicsHigh-speed laminar-turbulent transition

Research AreasHigh-speed laminar-turbulent transition is critical for applications including

hypersonic reconnaissance vehicles, thermal protection for re-entry vehicles, dragreduction on supersonic transports, and flow noise and heat transfer above IR windowson interceptor missiles. Unfortunately, nearly all existing high-speed experimentalresults are contaminated by facility noise, such as that radiating from the turbulentboundary layers normally present on the test-section walls of supersonic tunnels. Just asat low speeds, reliable experimental progress requires low-turbulence wind tunnels withnoise levels comparable to those in flight.



NASA Langley has developed quiet supersonic tunnels over the last 25 years toaddress problems such as laminar-turbulent transition that are strongly affected by noiselevel. Detailed measurements of the mechanisms of transition are needed, under lownoise conditions, in order to develop computational models that are grounded on thecorrect flow physics.

To complement the expensive quiet-flow facilities under development at NASALangley, a low-cost 4-inch Mach 4 quiet-flow Ludwieg tube has been constructed atPurdue. Quiet flow has been demonstrated to length Reynolds numbers of 400,000(AIAA Journal, April 1995, p. 688). Studies of the crossflow instability on an ellipticcross-section cone are now underway, using two forms of controlled perturbations (see,for example, AIAA Papers 96-2191, 98-0532, and 98-0436). Localized hot-spotdisturbances are repeatably generated by a pulsed Nd:YAG laser in order to generaterepeatable wave packets in the flow, and surface perturbations are being generated by aglow perturber. Perturbations are being measured using hot wires, high-sensitivity laserdifferential interferometry, and arrays of surface hot films.

A new 18-inch stainless-steel Ludwieg tube is being constructed, for use with an9.5-inch quiet-flow Mach-6 test section. Quiet-flow operation to a length Reynoldsnumber of 13 million is projected (AIAA Paper 98-0547). The air and vacuum systemsshould be complete by the end of summer 1998, with initial tunnel operation planned forSpring 1999. Modern digital and optical instrumentation will enable efficient use of thesix-second run-time, and the short duration keeps operating costs low. The larger testsection will enable testing with larger models and thicker boundary layers.

PublicationsEngblom, W. A., Goldstein, D. B., Ladoon, D., and Schneider, S. P., "Fluid Dynamics ofForward-Facing Cavity Flow," Journal of Spacecraft & Rockets, Vol. 34, pp. 437-444,June 1997.

Conference Proceedings, Presentations and Invited LecturesLadoon, D., Schmisseur, J., and Schneider, S.P., "Laser-Induced Resonance in a ForwardFacing Cavity at Mach 4," AIAA paper No. 97-0339, presented at the AIAA AerospaceSciences Meeting, Reno, NV, Jan. 1997.

Reed, H. L., Kimmel, R., Schneider, S.P., and Arnal, D., "Drag Prediction and Transitionin Hypersonic Flow," 1997 Symposium on "Future Aerospace Technology in Service tothe Alliance," in the workshop on "Hypersonic Experimental and ComputationalImprovement and Validation," April 1997. Also presented at the 28th AIAA FluidDynamics Conference & 4th AIAA Shear Flow Control Conference, AIAA Paper No. 97-1818, Snowmass Village, CO, (17 pages), June 29-July 2, 1997.


Ladoon, D. W., and Schneider, S. P., "Instability and Transition Experiments at Mach 4Using an Electrical-Discharge Perturber," ASME paper FEDSM97-3112, in the 3rd

Symposium on Transitional and Turbulent Compressible Flows, ASME FluidsEngineering Conference, Vancouver, BC, (9 pages), June 1997.


JOHN P. SULLIVAN1975

Professor and Head

DegreesB. S., University of Rochester, Mechanical & Aerospace Sciences (with honors),

1967M. S., Massachusetts Institute of Technology, Aeronautical Engineering, 1969Sc.D., Massachusetts Institute of Technology, Aeronautical Engineering, 1973

InterestsExperimental aerodynamicsLaser instrumentationLuminescent sensors for temperature and pressure measurements

Research AreasCurrent research interest is in the area of experimental aerodynamics with

particular emphasis on comparison of experimental data with computational analysis.Current programs include:

1. High lift systems.2. Suction/blowing airfoils.

In addition to the above programs, work also continues on developing laserinstrumentation (laser Doppler velocimeter, particle image velocimeter, laser sheetconcentration, etc.) and pressure and temperature paint for:

1. Wind tunnels - low speed to hypersonic2. Gas turbine engines3. Flight tests


PublicationsAsai, K., Kanda, H., Kunimasu, T., Liu, T., and Sullivan, J. P., "Boundary-LayerTransition in a Cyrogenic Wind Tunnel Using Luminescent Paint," Journal of Aircraft,Vol. 34, No. 1, pp. 34-42, 1997.

Asai, K., Kanda, H., Kunimasu, T., Liu, T., and Sullivan, J. P., "Boundary-LayerTransition in a Cyrogenic Wind Tunnel Using Luminescent Paint," Journal of Aircraft,Vol. 34, No. 1, pp. 34-42, Feb. 1997.

Liu, T., Campbell, B. T., Burns, S. P., and Sullivan, J. P., "Temperature- and Pressure-sensitive Luminescent Paints in Aerodynamics," Applied Mechanics Review, Vol. 50, No.4, pp. 227-246, April 1997.

Conference Proceedings, Presentations and Invited LecturesHoffenberg, R., and Sullivan, J. P., "Simulation of High-Lift Wake Behavior," AIAA 97-0718, presented at the AIAA 35th Aerospace Sciences Meeting, Reno, NV, Jan. 6-10,1997.

Liu, T., and Sullivan, J. P., "Luminescent Oil-Film Skin Friction Meter," AIAA 97-2216,presented at the 15th AIAA Applied Aerodynamics Conference, Atlanta, GA, June 23-25,1997.

Liu, T., and Sullivan, J. P., "Applications of Temperature and Pressure Sensitive Paints,"presented at symposium on Advanced Aerodynamic Measurement Technology, Seattle,WA, Sept. 22-25, 1997.

Torgerson, S., Liu, T., and Sullivan, J. P., "Rotor Blade Pressure Measurements inRotating Machinery Using Pressure and Temperature Sensitive Paints," paper No. 19,presented at the 90th Meeting and Symposium of the Propulsion and Energetics Panel onAdvanced Non-Intrusive Instrumentation for Propulsion Engines, Brussels, Belgium, Oct.20-24, 1997.


MARC H. WILLIAMS1981

Professor

DegreesB. S., University of Pittsburgh, Aeronautical Engineering, Magna Cum Laude,

1969M. A., Princeton University, Aerospace & Mechanical Sciences, 1971Ph.D., Princeton University, Aerospace & Mechanical Sciences, 1975

InterestsAerodynamicsComputational fluid Mechanics

Research AreasThe determination of aeroelastic stability and forced response characteristics of

flight vehicles requires methods for predicting the unsteady aerodynamic loads that areinduced by structural deformation and/or free stream disturbances. Current research isdirected at developing such methods for transonic flight and for rotating machinery.

Much of this work has been done for advanced propfan applications. Theseengines are intended for use on medium range commercial transports, which operate atlow transonic Mach numbers. In order to maintain high operating efficiency and lownoise, the blades are very thin and flexible. Therefore they are subject to substantialstatic and dynamic deformations which alter the aerodynamic loads on the blades.Computational methods have been developed to predict these loads, both for single andcounter rotating systems. Flutter boundaries and forced vibration amplitudes have beensuccessfully predicted for a variety of current propfan designs. The most successfulschemes developed so far have been based on linearized aerodynamic models. Work is


under way on including nonlinear transonic effects through three dimensional potentialformulation with moving grids.


DYNAMICS & CONTROL


DOMINICK ANDRISANI1980

Associate Professor

DegreesB. S., Rensselaer Polytechnic Institute, Aeronautical Engineering, 1970M. S., State University of New York at Buffalo, Electrical Engineering, 1975Ph.D., State University of New York at Buffalo, Electrical Engineering, 1979

InterestsEstimationControlDynamicsFlight Aircraft Flying Qualities

Research AreasExtensive experience in experimental methods in the study of vehicle dynamics

and control has focused teaching and research on practical and important aerospaceproblems in four areas. First is the area of estimation theory, where new estimationalgorithms have been developed using the partitioning approach. The second areainvolves the application of estimation theory to aerospace problems. Here estimationtheory has been used to develop a new class of target trackers. These trackers incorporateknowledge of the aerodynamic and thrust vectors to help improve the trackers ability toestimate target acceleration. The third area involves research towards the development ofdesign specifications for helicopter flight control systems, i.e., helicopter flying qualities.The fourth area involves analysis and detection of pilot-in-the-loop oscillations.


Conference Proceedings, Presentations and Invited LecturesAndrisani, II, D. A., Conference Organizer for the "Annual Meeting of the Indiana SpaceGrant Consortium" (ISGC), Feb. 26, 1997.

Andrisani, II, D. A., "A Taste of Aerospace," presented at the Great Lakes RegionAviation and Space Education Conference, Dayton, OH, March 2, 1997.

Andrisani, II, D. A., "Careers in Aerospace," presented to North Vermillion MiddleSchool, North Vermillion, IN, April 11, 1997.

Andrisani, II, D. A., "A Taste of Aerospace," presented at the 1997 Meeting ofTechnology Educators of Indiana Meeting, Nashville, IN, April 18, 1997.

Peters, M. E., and Andrisani, II, D. A., "The Determination of Longitudinal FlyingQualities Requirements for Light Weight Unmanned Aircraft," AIAA Paper #97-3701,presented at the 1997 AIAA Guidance Navigation and Control Conference, New Orleans,LA, Aug. 11-13, 1997.

Andrisani, II, D. A., "The NASA Academy," presented at the First Meeting of theAeronautics Working Group of the National Council of Space Grant Directors, NASADryden, CA, Oct. 16-17, 1997.


MARTIN CORLESS1984

Professor

DegreesB. E., (1st honors), University College, Dublin, Ireland, Mechanical Engineering,

1977Ph.D., University of California, Berkeley, Mechanical Engineering, 1984

InterestsDynamicsSystemsControl

Research AreasMost of the research is concerned with obtaining tools which are useful in the

analysis and control of systems containing significant uncertainty. These uncertaintiesare characterized deterministically, rather than stochastically. The systems treated can belinear or nonlinear and continuous-time or discrete-time. The major application of theresearch is in the analysis and control of aerospace and mechanical systems. In theseapplications, some of the research focuses on the effect of flexible elements.

PublicationsCorless, M., and Leitmann, G., "Componentwise Bounded Controllers for RobustExponential Convergence," ASME Journal of Dynamic Systems, Measurement, andControl, Vol. 119, pp. 73-79, 1997.

D'Amato, F., Corless, M., Mattei, M., and Setola, R., "A Multivariable Stability Marginin the Presence of Time-Varying, Bounded Rate Gains," International Journal of Robustand Nonlinear Control, Vol. 7, pp. 127-143, 1997.


Corless, M., and Leitmann, G., "Destabilization via Active Stiffness," Dynamics andControl, Vol. 7, No. 3, pp. 263-268, 1997.

Corless, M., and Tu, J., "A Simple State/Uncertainty Estimator for a Class of UncertainSystems," Journal of the Brazilian Society of Mechanical Sciences, Vol. 19, No. 2, pp.176-191, 1997.

Zenieh, S., and Corless, M., "Simple Robust r-α Tracking Controllers for UncertainRobotic Manipulators," ASME Journal of Dynamic Systems, Measurement and Control,Vol. 119, No. 4, pp. 821-825, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsKendi, T. A., Brockman, M. L., Corless, M., and Doyle, F., "Controller Synthesis forInput-Constrained Nonlinear Systems Subject to Unmeasured Disturbances," 1997American Control Conference, Albuquerque, NM, 1997.

Corless, M., "Some Results in the Control of Flexible Mechanical Systems," Modellingand Control of Mechanical Systems, Imperial College, London, UK, 1997.


ARTHUR E. FRAZHOProfessor

1980

DegreesB.S.E., The University of Michigan, Ann Arbor, Computer Engineering, 1973M.S.E., The University of Michigan, Ann Arbor, Computer Information and

Control Engineering, 1974Ph.D., The University of Michigan, Ann Arbor, Computer Information and

Control Engineering, 1977

InterestsControl systems

Research AreasThis research develops and applies operator theory to problems in deterministic

and stochastic control systems. These techniques are used to design models for bothlinear and nonlinear control systems. We also obtain fast recursive algorithms forcomputing reduced order models. This also yields a theory of H∞ controller reductionand pole placement with applications to large space structure control. Finally, thesetechniques are used to solve problems in signal processing and inverse scattering theory.

PublicationsFoias, C., Frazho, A. E., Gohberg, I., and Kaashoek, M. A., "A Time-Variant Version ofthe Commutant Lifting Theorem and Nonstationary Interpolation Problems," IntegralEquation and Operator Theory, Vol. 28, pp. 158-190, 1997.


Foias, C., Frazho, A. E., Gohberg, I., and Kaashoek, M. A., "Parameterization of allSolutions of the Three Chains Completion Problem," Integral Equation and OperatorTheory, Vol. 29, pp. 455-490, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsSmith, M. J., and Frazho, A. E., " 2HH −∞ Control System Synthesis via LiftingTechniques," presented at the 31st Annual Conference on Information Sciences andSystems, John Hopkins University, Baltimore, MD, March 19-21, 1997.


KATHLEEN C. HOWELL1982

Professor

DegreesB. S., Iowa State University, Aerospace Engineering, 1973M. S., Stanford University, Aeronautical & Astronautical Engineering, 1977Ph.D., Stanford University, Aeronautical & Astronautical Sciences, 1983

InterestsOrbit mechanicsSpacecraft dynamics, controlTrajectory optimization

Research AreasIn the area of astrodynamics, the complex missions envisioned in the next few

decades will demand innovative spacecraft trajectory concepts and efficient design toolsfor analysis and implementation. In support of such plans, current research efforts focuson spacecraft navigation and maneuver requirements, and mission planning, both in theneighborhood of the Earth and in interplanetary space. Some sample projects arementioned below.

Much recent research activity has involved libration point orbits in the three- andfour-body problems. The n-body problem in orbital mechanics generally considerstrajectory solutions when (n-1) gravity fields are significant. Spacecraft in the vicinity oflibration points thus operate in an environment in which gravity forces due to two orthree (or more) celestial bodies may result in trajectories that appear as three-dimensional, quasi-periodic Lissajous paths. Such three-dimensional trajectories are ofconsiderable interest in connection with any future lunar operations. In the near term,missions involving libration point satellites are included in a number of programs that theU. S. is planning with international partners. Technical studies involve trajectory designand optimization including optimal control strategies for out-of-plane motion in


consideration of communication and other operational specifications. Analyses ofstation-keeping requirements for such trajectories are also currently under study.

The subject of optimal transfer trajectories is of considerable importance andrapidly growing in complexity as well. New types of problems now facing missiondesigners render standard optimization strategies inadequate, particularly for applicationin the n -body problem. Nominal transfer trajectory determination and optimization is thefocus of an expanding investigation. Various projects range from development of newcomputational techniques to application of geometric nonlinear dynamical systems theoryto these problems.

A related problem of interest involves Earth orbiting vehicles that repeatedly passclose to the Moon. Such trajectories use lunar gravity to effect trajectory changes. Notonly can such a swingby aid in minimizing mission fuel requirements, it also createstrajectory options that may otherwise be impossible. Analysis is complicated, however,by the strong solar perturbation. Multi-conic analysis has proven promising and work iscontinuing to develop tools to make optimal trajectory design efficient and accurate.Design strategies can also be extended to other multi-body systems. Such applicationsare under considerations as well.

PublicationsHowell, K. C., Barden, B. T., and Lo, M. W., "Application of Dynamical Systems Theoryto Trajectory Design for a Libration Point Mission," Journal of Astronautical Sciences,Vol. 45, No. 2, pp. 161-178, April-June 1997.

Ely, T. A., and Howell, K. C., "Dynamics of Artificial Satellite Orbits with TesseralResonances Including the Effects of Luni-Solar Perturbations," The International Journalof Dynamics and Stability of Systems , Vol. 12, No. 4, pp. 243-269, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsHowell, K. C., "Introducing Group Learning into a 'Lecture' Class," AIAA 35th


Ely, T. A., and Howell, K. C., "East-West Stationkeeping of Satellite Orbits withResonant Tesseral Harmonics," AAS/AIAA Space Flight Mechanics Meeting, Huntsville,AL, Feb. 1997.

Howell, K. C., "Application of Dynamical Systems Theory to Support TrajectoryDesign," Libration Point Mission Design Workshop, NASA Marshall Space FlightCenter, Huntsville, AL, Feb. 1997.

Howell, K. C., "Using Manifolds to Generate Trajectories for Libration Point Missions,"Fourth SIAM Conference on Applications of Dynamical Systems, Snowbird, UT, May1997.


Howell, K. C., Barden, B. T., Wilson R. S., and Lo, M. W., "Trajectory Design using aDynamical System Approach with Application to GENESIS," AAS/AIAAAstrodynamics Conference, Sun Valley, ID, Aug. 1997.


JAMES M. LONGUSKI1988

Associate Professor

DegreesB.S.E., The University of Michigan, Aerospace Engineering - Cum laude, 1973M.S.E., The University of Michigan, Aerospace Engineering, 1975Ph.D., The University of Michigan, Aerospace Engineering, 1979

InterestsSpacecraft DynamicsOrbit MechanicsControlOrbit decay and reentry

Research AreasCurrent research efforts include 1) analytic theory and control of spinning-up and

thrusting vehicles, 2) mission design and trajectory design for interplanetary flight, 3)orbit decay and reentry problems, and 4) tethers in space.

In 1) breakthroughs were achieved earlier at the Jet Propulsion Laboratory in theanalysis of the Galileo spacecraft maneuvers. The current goal is to extend this work to ageneral analytic theory (which provides solutions for angular velocity, the attitude, theangular momentum vector and the translational velocity of rigid and elastic bodiessubject to arbitrary body-fixed torques and forces) and to develop control laws based onthe analytic theory.


In 2) mission design tools developed at the Jet Propulsion Laboratory have beenacquired for research use at Purdue. Both theoretical and computational techniques arebeing employed to analyze the ∆V gravity-assist problem in terms of identifyingpotential trajectories (such as the Voyager Grand Tour and the Galileo VEEGA) andoptimizing the launch energy and propellant requirements for these trajectories.

In 3) analytic solutions have been obtained for the probability of immediatereentry and of orbit decay, as well as escape, in the event of misdirected interplanetaryinjection maneuvers occurring at low earth orbit. The solutions have relevance to safetyissues involving nuclear power plants aboard deep space probes.

In 4) the feasibility of using tethers for aerobraking has been demonstrated. Thebasic idea is to connect an orbiter and a probe together by a long tether, for missions toplanets with atmospheres. The probe enters the atmosphere and is used to reduce thehyperbolic speed of the orbiter to capture speed, thus eliminating the large retromaneuver normally required. New issues being addressed include analysis of the flexibletether, tether guidance and control, and spacecraft (endpoint) attitude control.

PublicationsSims, J. A., Longuski, J. M., and Staugler, A. J., " ∞V Leveraging for InterplanetaryMissions: Multiple-Revolution Orbit Techniques," Journal of Guidance, Control, andDynamics, Vol. 20, No. 3, pp. 409-415, May-June 1997.

Beck, R. A., and Longuski, J. M., "Annihilation of Transverse Velocity Bias DuringSpinning-Up Maneuvers," Journal of Guidance, Control, and Dynamics, Vol. 20, No. 3,pp. 416-421, May-June 1997.

Sims, J. A., Staugler, A. J., and Longuski, J. M., "Trajectory Options to Pluto via GravityAssists from Venus, Mars, and Jupiter," Journal of Spacecraft and Rockets, Vol. 34, No.3, pp. 347-353, May-June 1997.

Tragesser, S. G., Longuski, J. M., and Puig-Suari, J., "Global Minimum Mass forAerobraking Tethers," Journal of Guidance, Control, and Dynamics, Vol. 20, No. 6, pp.12160-1262, Nov.-Dec. 1997.

Book ChapterLonguski, J. M., "Aerocapture with Tethers for Planetary Exploration," Tethers in SpaceHandbook, Cosmo, M. L., Lorenzini, E. C., (eds), 3rd ed., Smithsonian AstrophysicalObservatory, Cambridge, MA, pp. 81-82, December 1997.

Conference Proceedings, Presentations, Invited Lectures, and ReportsKuchnicki, S. N., Tragesser, S. G., and Longuski, J. M., "Dynamics of a Tether Sling,"AAS Paper No. 97-605, AAS/AIAA Astrodynamics Conference, Sun Valley, ID, August4-7, 1997.


Tragesser, S. G., and Longuski, J. M., "Modeling Issues Concerning Motion of theSaturnian Satellites," AAS Paper No. 97-670, AAS/AIAA Astrodynamics Conference,Sun Valley, ID, August 4-7, 1997.

Beck, R. A., and Longuski, J. M., "Large Angle Solution for a Spinning Rigid BodySubject to Constant Transverse Torques," AAS Paper No. 97-680, AAS/AIAAAstrodynamics Conference, Sun Valley, ID, August 4-7, 1997.

Tragesser, S. G., and Longuski, J. M., "Saturn Gravity Field Modeling Accuracy, FinalReport prepared for Jet Propulsion Lab by Purdue University, JPL Contract No. 960620,23 pages, Sept. 30, 1997.

Tragesser, S. G., and Longuski, J. M., "Saturn Gravity Field Modeling Accuracy," FinalReport with Appendices prepared for Jet Propulsion Lab by Purdue University, JPLContract No. 960620, 47 pages, Dec. 1997.


MARIO A. ROTEA1990

Associate Professor

DegreesElectronic Engineer Degree (6-year curricula), Universidad Nacional de Rosario,

Argentina, 1983M.S.E.E., University of Minnesota, Electrical Engineering, 1988Ph.D., University of Minnesota, Control Science & Dynamical Systems, 1990

InterestsRobust and nonlinear multivariable controlModeling, identification, and control of flow and combustion instabilities;

turbomachinery; rotorcrafts; and manufacturing processes.

Awards and Major AppointmentsNSF Young Investigator Award

Research AreasBasic research in systems and controls is aimed at developing methods and tools

for controller design with multiple performance and robustness specifications, and thereal-time implementation of dynamical systems with time and amplitude quantizations.Recent applied research includes active control design for the suppression of instabilitiesin turbomachinery, machine tools, and rotorcrafts, and the development of a methodologyfor the design of low order controllers in civil engineering structures. This basic andapplied research has been partially supported by NSF, United Technologies Corporation,and Boeing Company.


PublicationsZhu, G., Rotea, M. A., and Skelton, R. E., "A Convergent Algorithm for the OutputCovariance Constraint Problem," SIAM Journal on Control and Optimization, Vol. 35,No. 1, pp. 341-361, Jan. 1997.

Iwasaki, T., and Rotea, M. A., "Rank-one Scaled ∞H Optimization," Transactions of theASME: Journal of Dynamic Systems, Measurement, and Control, Vol. 119, No. 3, pp.513-520, Sept. 1997.

Iwasaki, T., Hara, S., and Rotea, M. A., "Computational Complexity Reduction in Scaled

∞H Synthesis," Automatica, Vol. 33, No. 7, pp. 1325-1332, 1997.

Iwasaki, T., and Rotea, M. A., "Fixed Order Scaled ∞H Synthesis," Optimal ControlApplications and Methods, Vol. 18, No. 5, pp. 381-398, 1997.

Prasanth, R., and Rotea, M. A., "Interpolation with Multiple Norm Constraints,"Mathematics of Control, Signals, and Systems, Vol. 10, No. 2, pp. 165-187, 1997.

Conference Proceedings, Presentations, Invited Lectures, and ReportsViassolo, D., and Rotea, M. A., "Optimal Scaling of Digital Controllers," Proc. 1997American Control Conference, Vol. 6, pp. 3611-3625, 1997.

Prasanth, R. K., and Rotea, M. A., "Design Tools for Multiobjective ∞H Control," Proc.AIAA Guidance, Navigation, and Control Conference, New Orleans, LO, Vol. 3, pp.1270-1279, 1997.

Rotea, M. A., and Marchetti, J., "Integral Control of Heat-Exchange-Plus-BypassSystems," Proc. IEEE International Conference on Control Applications, Hartford, CT,pp. 151-156, 1997.

D'Amato, F., and Rotea, M. A., "Limits of Achievable Performance and ControllerDesign for the Structural Control Benchmark Problem," IEEE Conference on ControlApplication, Hartford, CT, pp. 547-552, 1997.

Rotea, "Fourth-Annual NSF-YIA Progress Report," Grant No. ECS-93-58288, May1997.

Gysling, D., Jacobson, C. A., Rey, G., and Rotea, M. A., "Identification and Validation ofUTRC Flutter Model," presentation at the AFOSR-PRET Workshop on Robust Controlof Aeroengines, Univ. of California, Santa Barbara, CA, Jan. 1997 (closed session).

Gysling, D., Jacobson, C. A., Rey, G., and Rotea, M. A., "Experimental Results on theUTRC 17-inch Flutter Rig," presentation at the AFOSR-PRET Workshop on Robust


Control of Aeroengines, Univ. of California, Santa Barbara, CA, Jan. 1997 (closedsession).

Rotea, M. A., "Workshop on Future Directions in Systems and Control," DiscussionLeader in Prof. Goodwin's talk, Univ. of Illinois at Urbana-Champaign, Monticello, IL,Sept. 1997.

Rotea, M. A., "Limits of Achievable Performance and Controller Design for theStructural Control Benchmark Problem," Computer Integrated Process Operations Center(CIPAC) Seminar Series, School of Chemical Engineering, Purdue Univ., W. Lafayette,IN, April 1997.


PROPULSION


STEPHEN D. HEISTER1990

Associate Professor

DegreesB.S.E., The University of Michigan, Aerospace Engineering, 1981M.S.E., The University of Michigan, Aerospace Engineering, 1983Ph.D., Univ. of California at Los Angeles, Aerospace Engineering, 1988

InterestsRocket propulsionLiquid propellant injection systems

Research AreasCurrent research interests in the field of propulsion are aimed at increasing

understanding of liquid injection processes and combustion in hybrid rocket systems.

Liquid jet atomization is a problem of fundamental importance in liquid andhybrid rocket engines, as well as in airbreathing engines or any other device using liquidfuel. The focus of our research is to develop numerical models capable of describing thetime-dependent, non-linear evolution of liquid jet surface as the jet exists the orifice. Theanalytic approach involves the use of Boundary Element Methods, which are an attractivetool for problems involving free surfaces. Initial modeling efforts have focused oninviscid flows with negligible gas phase interaction. In the near future, the presence ofthe gas phase will be included in models, and in coming years we shall consider the effectof liquid viscosity on the complex atomization process.

Another area of research involves modeling of the flow processes inside an orificeof a high pressure injector. In liquid rocket and diesel engines, the injection pressures


can be high enough to cause cavitation within the injector passages thus leading to pittingof injector surfaces and changes in spray quality. We are developing numerical modelsto describe this two-phase (and possibly unsteady) flow process. Current efforts areunderway to extend our axisymmetric model to three dimensions in order to analyzeflows in diesel injectors manufactured by Cummins Engines Incorporated of Columbus,Indiana.

A promising new area of research involves experimental determination of thecombustion characteristic of hybrid rocket engines using concentrated hydrogen peroxideas an oxidizer. An experimental facility has been constructed for the purpose of theseactivities.

Sponsored Research Summaries1. Atomization modeling - Under AFOSR sponsorship, a number of atomization modelshave been developed to study the unsteady evolution of liquid jets and droplets. Thesesimulations utilize boundary element methods to provide high-resolution of very largesurface distortions and atomization processes. In fact, a number of the models can carryout calculations beyond atomization events. Most recently, we have coupled theboundary element solutions with an integral method treatment of the boundary layer inorder to investigate viscous effects in high-speed jets. In addition, a fully three-dimensional code is in development and should be completed in mid-1997. As a result ofthese developments, we have modified existing models to address electrostatic forces andare currently working a project (with Professor Sojka of Mechanical Engineering) onelectrostatic atomization. This effort is funded by Proctor and Gamble.

2. Hybrid Rocket Combustion Experiments - This effort involves the use of the PurdueUniversity Rocket Propulsion Lab (PURPL); a facility housed at the Thermal Sciencesand Propulsion Center. Currently, lab scale motors are being fired to assess basiccombustion phenomena in hybrid rockets. We currently utilize hydrogen peroxide andpolyethylene as oxidizer and fuel, respectively. Over 100 firings of this propellantcombination have been conducted during the past three years. Due to the high level ofinterest in the clean burning, safe handling aspects of hydrogen peroxide, numerous otheropportunities are being investigated for potential application in the PURPL facility.

3. Diesel Engine Injector Modeling - This project, funded by Cummins EngineCompany and NSF, is aimed at developing computational tools for use in simulatinginternal flows in diesel injector passageways. Due to the high injection pressures,cavitation is a crucial feature which must be incorporated in the modeling. To this end,we have developed a new cavitation treatment capable of addressing hydrodynamicnonequilibrium effects in a fully viscous calculation. The model is currently beingupgraded to improve efficiency and to ultimately extend capabilities to address 3-Dflows. In addition, 2-D simulations are underway to calibrate the tool against flowfieldmeasurements being obtained by Professor Collicott’s research group.


PublicationsHeister, S. D., and Messersmith, N. L., "Launch Competition for Rocket PropulsionEducation," International Journal of Engineering Education, Vol. 12, No. 3, 1997.

Heister, S. D., Rutz, M., and Hilbing, J., "Effect of Acoustic Perturbations on Liquid JetAtomization," Journal of Propulsion and Power, Vol. 13, No. 1, pp. 82-88, 1997.

Heister, S. D., "Boundary Element Methods for Two-Fluid Free Surface Flows,"Engineering Analysis with Boundary Elements, Vol. 19, No. 4, pp. 309-317, 1997.

Setiawan, E., and Heister, S. D., "Nonlinear Modeling of an Infinite Electrified Jet,"Journal of Electrostatics, Vol. 42, pp. 243-257, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsWernimont, E. J., and Heister, S. D., "Experimental Study of Chamber Pressure Effectsin a Hydrogen Peroxide-Oxidized Hybrid Rocket," AIAA 97-2801, 33rd AIAA JointPropulsion Conference, 1997.

Rump, K. M., and Heister, S. D., "Modeling the Effect of Unsteady Chamber Conditionson Atomization Processes," AIAA 97-3298, 33rd AIAA Joint Propulsion Conference,1997.

Setiawan, E., and Heister, S. D., "Nonlinear Modeling of an Infinite Electrified Jet,"ILASS-97 Conference Proceedings, 1997.

Heister, S. D., "Modeling Atomization Processes," 52nd Annual Industrial WasteConference Proceedings, 1997.


STRUCTURES & MATERIALS


WILLIAM A. CROSSLEY1995

Assistant Professor

DegreesB.S.E. University of Michigan, Aerospace Engineering, 1990M. S. Arizona State University, Aerospace Engineering, 1992Ph.D. Arizona State University, Aerospace Engineering, 1995

InterestsOptimizationRotorcraft and aircraft designStructure design

Research AreasGenetic Algorithms (GA) are a relatively new class of search and optimization

methods that mimic the idea of natural selection displayed by biological populations.The idea of "fitness" is analogous to an objective function in a more traditionaloptimization method. GA can use this idea of fitness to find solutions to optimal designproblems that are difficult or impossible to solve using calculus-based methods.Research is being conducted to apply GA to a wide range of aerospace-related problemsand to develop appropriate GA schemes for multiobjective and constrained optimization.

The abilities of genetic algorithms also allow them to perform as automateddesign methodologies. Combining selection and sizing tasks for rotorcraft conceptualdesign in a GA-based approach has demonstrated the ability of the genetic algorithm togenerate designs for helicopters in much the same manner as human designers. Work iscontinuing to increase the applicability of this automated design approach to bothrotorcraft and fixed-wing aircraft.


Recent investigation of smart materials and structures has displayed the potentialfor these concepts to be applied to aircraft in a variety of ways. Preliminary investigationof smart structures for adaptive rotor systems to improve primary rotor performance isbeginning. Design techniques for these smart structures in aerospace systems are beingdeveloped.


Topology Design of Rotor Blades for Aerodynamic and Structural Concerns. Thiscomputational research effort strives to develop a new and unique rotor blade designstrategy with the potential to improve the aerodynamic, structural and dynamicperformance of advanced rotorcraft. This work will investigate the use of a GeneticAlgorithm (GA) as the means to combine aerodynamic and structural concerns fortopology design of rotor blades. Inverse airfoil design and optimal airfoil design arereceiving much attention in both industry and academia; the same holds true for structuraloptimization. The combination of the two concerns for topology design has not beenfully addressed. A multidisciplinary approach combining structural and aerodynamicconcerns for optimal topology design of rotor blades provides potential benefit to therotorcraft design process. To demonstrate this new design method, blades will bedesigned for a prop-rotor, like that for the envisioned Short Haul Civil Tiltrotor.(Sponsored by NASA Ames Research Center Graduate Student Researcher Program;David Fanjoy, graduate student)

Development of a Genetic Algorithm for Conceptual Design of Aircraft. Air vehicleconceptual design appears to be a promising area for application of the genetic algorithmas an approach to help automate part of the design process. This approach can reducesome of the subjective decision-making often associated with conceptual design, whilealso determining optimal parameter values for the aircraft. Work has been extensivelyconducted for helicopters, some additional work has been conducted for high-speedVTOL rotorcraft (e.g. tilt-rotor and tilt-wing aircraft), and work is currently beginning forfixed-wing aircraft. Because the GA-based approach to conceptual design helps toreduce the number of qualitative decisions needed from the design team, this appears tohave great potential for application to aircraft design. This is particularly true for aircraftwhose configurations may be significantly different than current aircraft, such asV/STOL aircraft, unmanned (UAV) and remotely piloted vehicles (RPV). (Sponsored byPurdue Research Foundation Grant; Greg Roth, graduate student)

Application of Genetic Algorithms to Hybrid Rocket Booster Design. Hybrid rocketshave recently garnered much attention as cost-effective means for launch vehicleboosters. The ability of the hybrid to be throttled and a high specific impulse make thehybrid appealing compared to solid-rocket boosters, while the use of a single liquid offersgreater simplicity in construction and operation than liquid bi-propellant systems.Performance of a hybrid rocket depends greatly on continuous variables like chamberpressure and oxidizer mass fuel rate; however, integer and discrete variables like thenumber and shape of fuel ports and choice of oxidizer and fuel system, also impact the


rocket’s performance. Because of this combination of design variables, this problemappears well suited to the genetic algorithm. Research is being conducted to determineappropriate GA techniques for hybrid rocket boosters. (Prof. Heister, co-investigator;Philip Schoonover, graduate student)

Genetic Algorithm Operator Development for Improved Satellite Constellation Designand Optimization. Improving satellite constellation design is of great interest to any usersof satellite communication (e.g. cellular phones, television), location (e.g. globalpositioning system) and/or observation (e.g. weather). Many of today’s satelliteconstellation designs rely on the “Walker Constellations”, a series of designs developedin 1970, which have rarely been improved upon. This research investigates new methodsfor satellite constellation design for distributed satellite systems. Based on preliminaryefforts, it appears that global optimization techniques can be a great help in the optimaldesign of satellite constellations, and this proposed effort will provide research necessaryto advance this work in order to determine optimum conditions for use of a distributedsatellite system. Additionally, the ability to address constellation performance (coverage)issues and the cost of assembling the constellation (∆V) will be incorporated into theoptimization approach. To support this effort, new approaches for orbit analysis andcoverage calculations will be developed with the intent of reducing analysis time to makethese routines suitable for use with a global optimization routine. (Edwin Williams,graduate student)

Aerodynamic and Aeroacoustic Optimization of Airfoils via a Parallel GeneticAlgorithm. A parallel genetic algorithm (GA) was used to generate, in a single run, afamily of aerodynamically efficient, low-noise rotor blade designs representing the Paretooptimal set. The n-branch tournament, uniform crossover genetic algorithm operates ontwenty design variables, which constitute the control points for a spline representing theairfoil surface. The GA takes advantage of available computer resources by operating ineither serial mode or “manager/worker” parallel mode. The multiple objectives of thiswork were to maximize lift-to-drag of a rotor airfoil shape and to minimize an overallnoise measure including effects of loading and thickness noise of the airfoil. Constraintsare placed on minimum lift coefficient, pitching moment and boundary layerconvergence. The program XFOIL provides the aerodynamic analysis, and the codeWOPWOP provides the aeroacoustic analysis. The Pareto-optimal airfoil set has beengenerated and is compared to the performance of a typical rotorcraft airfoil underidentical flight conditions. (Prof. Lyrintzis, co-investigator; Brian Jones, graduatestudent)

Methods to Assess Commercial Aircraft Technologies. The lack of a clear technologydevelopment strategy in today’s commercial aircraft industry warrants the developmentof a methodology to assess new technologies in terms of both cost and performance. Thepurpose of this study is to provide an effective means of evaluating a large number oftechnologies for commercial transport aircraft without a large expenditure of the airframemanufacturer’s research and development budget. The work encompasses technologiesthat can be applied to the aircraft design and technologies that improve the development,manufacturing and testing of the product. This is a departure from past studies that tendto focus on a small number of performance-based technologies. This work takes input


from experts in various engineering disciplines and evaluates technology in terms ofseveral cost measures: airline profit, unit cost, trip operating cost, recurring cost to build,and nonrecurring cost to build. The methodology is divided into two phases. The firstphase evaluates technologies based on cost alone. The second phase of this workredesigns an aircraft with new technologies, assesses the relative importance ofperformance-based technologies, and recognizes technology interactions using Taguchi’sDesign of Experiments. The study identifies promising technologies for further studyand recommendations can be made based on the results. (Partially supported by theNational Science Foundation / Purdue University Center for CollaborativeManufacturing; Tamaira Ross, graduate student)

PublicationsCrossley, W. A., and Laananen, D. H., "The Genetic Algorithm as an AutomatedMethodology for Helicopter Conceptual Design," Journal of Engineering Design, Vol. 8,No. 3, pp. 231-250, Sept. 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsCrossley, W. A., "Genetic Algorithm with the Kreisselmeier-Steinhauser Function forMultiobjective Constrained Optimization of Rotor Systems," AIAA paper No. 97-0080,AIAA 35th Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 6-9, 1997.

Crossley, W. A., and Williams, E. A., "A Study of Adaptive Penalty Functions forConstrained Genetic Algorithm Based Optimization," AIAA paper No. 97-0083, AIAA35th Aerospace Sciences Meeting and Exhibit, Reno, NV, Jan. 6-9, 1997.

Crossley, W. A., "Genetic Algorithm-Based Optimization for Stiffened CompositePanels," presented at McDonnell Douglas Helicopter Systems, Mesa, AZ, Jan. 10, 1997.

Crossley, W. A., "Genetic Algorithms for Engineering Design and Optimization: AnIntroduction," six-hour short course presented to The Aerospace Corporation, ElSegundo, CA, March 10-11, 1997.

Fanjoy, D. W., and Crossley, W. A., "Aerodynamic Topology Design for Rotor Airfoilsvia Genetic Algorithm," Proceedings of the 53rd Annual Forum of the AmericanHelicopter Society, Virginia Beach, VA, Vol. 3, pp. 144-152, May 1, 1997.

Crossley, W. A., "Genetic Algorithms for Engineering Design and Optimization,"seminar presented at Hughes Space Company, Los Angeles, CA, June 2, 1997.

Williams, E. A., and Crossley, W. A., “Empirically-Derived Population Size andMutation Rate Guidelines for a Genetic Algorithm with Uniform Crossover,” WSC2: 2nd

On-line World Conference on Soft Computing in Engineering Design andManufacturing, June 23-27, 1997.


Crossley, W. A., "Engineering Design and Optimization with Genetic Algorithms," guestlecture to CSCE 886-Evolutionary Algorithms, Air Force Institute of Technology,Wright-Patterson AFB, OH, Aug. 6, 1997.

Crossley, W. A., "Engineering Design and Optimization with Genetic Algorithms,"Allison Advanced Development Co., Indianapolis, IN, Aug. 22, 1997.


JAMES F. DOYLE1977

Professor

DegreesDipl. Eng., Dublin Institute of Technology, Ireland, 1972M.Sc., University of Saskatchewan, Canada, 1974Ph.D., University of Illinois, 1977

InterestsStructural dynamicsExperimental MechanicsInverse ProblemsWave propagation

Research AreasWave Motion in Structures

Because of their size and low stiffness, large space structures are susceptible towave motions due to transients. New, spectrally formulated, elements are beingdeveloped that are suitable for dynamic problems and have the following advantages:

Single elements can extend from joint to joint thus giving a remarkable reductionin the size of the system to be solved (with no loss of resolution.)

Inverse problems can be solved conveniently, thus making it useful forexperimental systems identification studies.


Experimentally characterized substructures (such as joints) may be easily incorporated in the modeling.

Spectral elements have already been developed for rods, beams and shafts, andtheir implementation in a general 3-D structural analysis computer programaccomplished.

Impact and Damage of StructuresA very important aspect of structural performance is the ability to withstand

impact and minimize the amount of damage caused. Impact had two effects on damage:(1) Generation if new damage near the impact site or at a stress concentrator. (2)Increased damage at pre-existing flaws caused by the propagated energy. Currentinvestigations involve wave interactions with delamination flaws. This has directapplication to damage in composite materials. Other aspects of the problem include:

FORCE IDENTIFICATION: from measurements made on the structure beingable to determine the impact of force history.

REMOTE SENSING: from analysis of the reflected and transmitted waves beingable to locate flaws and estimate their size.

LOCAL/GLOBAL ANALYSIS: separate the global structural dynamics from thelocal behavior near the flaw, thus leading to computational efficiencies. A novel layeredspectral element has been developed for use with composite materials.

Whole Field Image CharacterizationAn alternative to strain gages and accelerometers in dynamic measurements is to

use ultra-high speed photography coupled with such methods as photoelasticity; andmoiré. The question being investigated is: Under what circumstances is a single (or alimited number) of photographs capable of completely characterizing the waveinformation? This touches on some fundamental aspects of transform theory coupledwith measurement theory. The payoff is that photographs combined with digital imagingtechniques offer unique possibilities for recording and post-processing the data. This isessentially an experimental problem because experimental data is always incomplete, soquestions of quality of the data, the amount of data, etc. must be confronted, as well asthe following aspects: (1) High-Speed photography and photoelasticity (2) Digitalimaging techniques (3) @-D Fast Fourier Transforms.

PublicationsKannal, L. E., and Doyle, J. F., "Combining Spectral Super-Elements, GeneticAlgorithms, and Massive Parallelism for Computationally Efficient Flaw Detection inComplex Structures," Computational Mechanics, 1997.

Martin, M. M., and Doyle, J. F., "Estimation of Crack Location and Size in FrameStructures using Dynamic Response Measurements," Experimental Mechanics, 1997.


Doyle, J. F., "A Wavelet Deconvolution in Method for Impact Force Identification,"Experimental Mechanics, Vol. 37, pp. 403-408, 1997.

BookDoyle, J. F., Wave Propagation in Structures, Springer-Verlag, New York, 1989, 2nd

edition Summer 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsKannal, L. E., and Doyle, J. F., "Sub-Domain Inverse Methods," SEM Proceedings,Nashville, TN, June 1997.

Doyle, J. F., "Acoustic Wave Propagation through Complex Structures," Proceedings 6th

International Conference on Structural Dynamics, ISVR, Southampton, July 1997.

Doyle, J. F., "Spectral Super Elements for Efficient Damage Detection in ComplexStructures," Proceedings of the 14th U. S. Army Symposium on Solid Mechanics, 1997.


HORACIO D. ESPINOSA1992

Associate Professor

DegreesSc.B., Northeast National Univ., Magna Cum Laude, Civil Engineering,

Argentina, 1981Sc.M., Polytechnic of Milan, Italy, Structural Engineering, 1987Sc.M., Brown University, Solid Mechanics, 1989Sc.M., Brown University, Applied Mathematics, 1990Ph.D., Brown University, Solid Mechanics, 1992

Honors and Awards• ONR-YIP Award, 1997• NSF-CAREER Award, 1996• NSF-Research Initiation/Instrumentation Awards, 1993

Research Interestsa. Development of novel experiments with interferometric diagnostic techniques

including full field velocity and temperature measurements.

b. Dynamic propagation of cracks in brittle solids. Examination of critical conditionsfor crack initiation and propagation. Speckle and Moire′ techniques applied to cracktip dynamic measurements.

c. Microcracking and inelasticity of brittle materials. Identification and modeling offailure mechanisms. Effect of grain size, second phases, and texture on the dynamicresponse of ceramics and glasses.


d. Tribomechanics and machining of nanostructured materials. Assessment of localinelasticity, microplasticity and microcracking, in the frictional behavior of interfacesas a function of surface characteristics and lubrication.

e. High temperature dynamic testing and modeling of ceramic tailored microstructures.Derivation of multidimensional constitutive models.

f. Plastic flow and shear localization in amorphous materials.

g. Computational algorithms for parallel computing, mesh adaptivity, and discretefragmentation.

Research AreasResearch interests are in the area of constitutive modeling, dynamic failure and

wave propagation studies in ceramics and composites. These materials have attracted agreat deal of attention because of their outstanding, often unique, properties that allowthem to perform a wide variety of functions. For instance, ceramics are emergingmaterials with a great potential in applications such as thermal spray coatings, turbineblade coatings, cutting tools, wear parts, sensors, magnetic recording media, structuraland electronic components, multi-layered armor, and pharmaceutical/medical systems(e.g., alumina prosthetic articulating joints). In all these applications fundamentalunderstanding of their mechanical properties and failure mechanisms is needed. In anattempt to properly characterize the mechanical response of these advanced materials, aunique experimental and computational approach is being pursued.

• Experimental and Computational MechanicsOur research involves the testing of ceramics and composites under a variety of

impact loading configurations. The experimental technique consists of generating normaland shear waves with a time resolution of a few nanoseconds and magnitudes up toseveral gigapascals (GPa), in specially designed target plates. In the case of recoveryexperiments, postshock examination of the specimens by means of electron microscopyand other observational methodologies, allows the identification of inelasticity anddamage. These observations form the bases for (i) the comprehensive understanding ofprocesses (microcracking, phase transformations, microplasticity) occurring at themicrostructural level and (ii) the formulation of physically based constitutive models.Interferometric records, performed during the wave propagation event, are used as adiagnostic tool in the examination of derived or postulated models. In addition, cellcalculations of random microstructures are performed to identify the role of grain size,grain boundary structure, second phases and grain morphology in the failure mechanisms.Our numerical simulations account for crystal elastic and thermal anisotropy, grainplasticity, and grain boundary decohesion. The primary goal of this research is thederivation of continuum multiple-plane models that can predict macroscopic materialbehavior and in particular failure due to damage or shear localization.

Computer simulations of experiments conducted in our Dynamic InelasticityLaboratory are performed. The simulations examine the role of microstructure,deformation rate, and state of multi-axial loading in the interpretation of wavefront


attenuation, pulse spreading, and damage induced anisotropy. An explicit finite elementcode incorporating finite deformations, inelasticity, contact between bodies, and adaptivemeshing is used. Furthermore, novel wave propagation experiments are underdevelopment to extend the impact technique to penetration mechanics, dynamic friction,and material instability studies.


Effect of Grain Size and Second Phases in the Dynamic Failure of Ceramics(Sponsored by the National Science Foundation; students and post-docs: Pablo D.Zavattieri, Sunil Dwivedi)

General objectives of the research are: 1) to numerically investigate the effect ofceramic microstructures on failure mechanisms through simulation of cells containing adistribution of grains with random and preferred orientations, second phases in the formof particles and/or thin intergranular layers with or without glass pockets, 2) to conductimpact recovery experiments that will enable microscopic observations and theinterferometric recording of velocity histories. This experimental/computationalapproach will be used to assess and model inelasticity in ceramic materials. Theinvestigation will be extended to the study of material behavior at high temperatures.Such research is of high priority because it will allow the use of ceramics and ceramiccomposites in engine components. An instrumentation proposal from the Air ForceOffice of Scientific Research (AFOSR) was awarded for this study.

Dynamic Friction Studies on Nanostructured Materials (Sponsored by NSFthrough young investigator award NSF-Career; students and post-docs: AlejandroPatanella, Y. Xu)

This research is being supported by an NSF-CAREER award. Research objectivesare the assessment of the role of local inelasticity, microplasticity and microcracking inthe frictional behavior of interfaces as functions of surface characteristics andlubrication. Moreover, the development of a finite element code capable of predictingmechanistic aspects of friction and wear will be pursued. Basic understanding offrictional behavior at interfaces will be gained by performing pressure-shear experimentsat pressures, slipping velocities, temperatures and surface roughnesses typical ofmanufacturing processes. The pressure-shear soft-recovery technique we developed,offers the additional and unique feature of allowing a correlation between dynamicloading of the interface and microstructural features observed on recovered samples at thesurfaces of interest. This information will be used in the formulation of sliding andfriction models, and their performance will be assessed through numerical simulations ofthe plate impact experiment. Cell calculations of random microstructures will beperformed to gain insight into the effects of grain size, grain boundary structure, andgrain anisotropy and orientation on the frictional behavior of brittle materials.

Damage and Energy Dissipation Mechanisms in Ballistic Impact (Sponsored bythe U.S. Army Research Office; students and post-docs: H-C. Lu and Gang Yuan)

In many ballistic impact test, often only the incident and residual velocities arerecorded. To understand the penetration process, recording the complete velocity historyof the projectile is highly desired. Professor Espinosa and his students developed an


experimental technique using laser interferometry to measure the surface motion of boththe projectile and the target plate. Penetration experiments will be conducted with a lightgas gun. The projectile holder is designed such that a normal velocity interferometer canbe obtained on a laser beam reflected from the back surface of the projectile. In additionto this measurement a multi-point velocity interferometer will be utilized to continuouslyrecord the motion of the target back surface. In order to obtain full field out-of-planedisplacement gradients, a shearing interferometric technique will be used. In thistechnique a laser beam reflected from the specimen surface is diffracted by two gratingsseparated by a fixed distance and filtered by a lens and a screen. A high-speed digitalcamera records the out-of-plane displacements. Research will focus on thecomprehensive understanding of failure mechanisms and the formulation of physicallybased micromechanical models. Delamination history, fiber breakage, and membraneeffects will be examined. Rate effects on these failure mechanisms will be systematicallyinvestigated. A numerical algorithm to simulate penetration experiments in multi-layeredtargets will be developed. A Lagrangian FEM with dynamic contact, and finitedeformation capabilities is currently under development. The contact law has beenaugmented with a decohesion law to simulate delamination and friction between plies.

Dynamic Delamination under Compression-Shear (Sponsored by the U.S.Army Research Office; students and post-docs: G. Emore, H-C. Lu, and Sunil Dwivedi)

The objective of this research is to investigate shear induced delamination in fiberreinforced composites, when compressive tractions are superimposed, and to formulate acontact model with decohesion law to simulate delamination and friction. Understandingcritical conditions for dynamic crack propagation in composite interfaces is essential inthe design of composite materials and structures. Crack initiation and propagationbetween plies in fiber composites, as a function of interface properties and remoteloading, will be examined. Furthermore, the existence of a critical energy release rate asa function of load mixity will be investigated. Knowledge of dynamic fracture toughnessof interfaces under mixed-mode loading conditions is very limited, mainly because of thedifficulties involved in the design of appropriate experiments. The methodologyproposed here consists of manufacturing of a crack-like defect in half of the interfaceplane by means of established manufacturing processes. This design will allow the studyof crack propagation in composite interfaces under well defined dynamic loadingconditions. By proper selection of plate thicknesses and angles of impact, pure shear,pure tension, and combined loading can be achieved. The precise stress field for crackinitiation, as a function of mode-mixity, will be identified by monitoring the emanatingwaves from the crack-tip. Velocity measurements will be accomplished by means of avariable sensitivity displacement interferometer (VSDI). The structure of the interfaceand its defects at the crack tip will be identified through electron microscopy studies.Furthermore, 3-D finite element numerical simulations of the dynamic event will beperformed with a contact/cohesive law in order to identify interface toughness.

Dynamic Fracture Toughness of Propagating Cracks in Brittle and NanoMaterials (Sponsored by the Office of Naval Research through a young investigatoraward, ONR-YIP; post-doc: Y. Xu)

The effect of loading rate in failure mode transition in steel has been successfullystudied. No such studies exist for the case of brittle and nano-materials. The researchefforts towards the understanding of size and material microstructure effects in brittle


failure can be significantly augmented by the study of dynamically loaded cracks.Professor Espinosa proposed to investigate failure modes by means of the impact ofprecrack specimens. A laser speckle technique will be used to examine strain fieldssurrounding cracks in ceramics and glasses. A light gas gun will be employed todynamically load the samples. Real time specklegrams will be recorded in a high-speedcamera. View area, and frame rate will be selected to measure grain plasticity, grainboundary shearing, and crack tip damage. A ceramic with tailored microstructure with anaverage grain size of 100-150 µm will be investigated. Fluorescent coatings will be usedto obtain temperature fields.

PublicationsEspinosa, H. D., Mello, M., and Xu, Y., "A Variable Sensitivity DisplacementInterferometer with Application to Wave Propagation Experiments," Journal of AppliedMechanics, Vol. 64, pp.123-131, 1997.

Espinosa, H. D., Xu, Y., and Brar, N. S., "Micromechanics of Failure Waves in Glass:Experiments," Journal American Ceramics Society, Vol. 80, No. 8, pp. 2061-2073, 1997.

Espinosa, H .D., Xu, Y., and Brar, N. S., "Micromechanics of Failure Waves in Glass:Modeling," Journal of American Ceramics Society, Vol. 69, No. 21, pp. 2074-2085,1997.

Espinosa, H. D., Xu, Y., and Lu, H.-C., "Inelastic Behavior of Fiber CompositesSubjected to Out-of-Plane High Strain Rate Shearing, Acta Materialia, Vol. 45, No. 11,pp. 4855-4865, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsEspinosa, H. D., "Development of a Microcracking Multiple-Plane Model for BallisticImpact, final progress report prepared for the U. S. Army Research Office, March 1997.

Espinosa, H. D., Lu, H.-C., Dwivedi, S., and Zavattieri, P. D., "A Finite DeformationAnisotropic Plasticity Model for Fiber Reinforced Composites," Proceedings of 12th

Annual Technical Conference of the American Society for Composites, Michigan, 1997.

Xu, Y., and Espinosa, H. D., "Damage Quantification in Confined Ceramic," ShockCompression of Condensed Matter, APS Conference, Amherst, MA, 1997.

Brar, N. S., Espinosa, H. D., Yuan, G., and Zavattieri, "Experimental Study of InterfaceDefeat in Confined Ceramics," Shock Compression of Condensed Matter, APSConference, Amherst, MA, 1997.

Espinosa, H. D., "Instrumentation for High Temperature Testing of Advanced Materials,final progress report prepared for AFOSR, March 1997.


THOMAS N. FARRIS1986

Professor

DegreesB.S., Rice University, Cum Laude, Mechanical Engineering, 1982M.S., Northwestern University, Theoretical and Applied Mechanics, 1984Ph.D., Northwestern University, Theoretical and Applied Mechanics, 1986

InterestsTribologyManufacturing processesFatigue and fracture

Research AreasIn tribology, a major research effort is underway in the experimental and

analytical characterization of fretting fatigue. The experimental work uses a uniquefixture design that allows independent control of the applied clamping and tangentialforces. Analytical work combines boundary and finite element analysis of the effect offorces, microslip, and geometry on subsurface stresses. Multiaxial fatigue theories arebeing used to correlate these stresses with experimentally observed crack nucleation andfracture mechanics is used to predict growth of these cracks. The calculations will thenbe used to predict the effect if fretting on multi-site damage nucleation and growth in theaging aircraft problem. The approach is being used to address fretting fatigue in jetengines as part of the Air Force High Cycle Fatigue initiative.

Manufacturing process research includes experimental and analytical work ongrinding and super finishing of hardened steels and ceramics for precision components.


The focus is on understanding the mechanics of the material removal process so that theeffect of process parameters on component performance can be predicted. To this end,deformation induced during the controlled static and sliding microindentation is beingstudied. An example of the results of this research is a recently established relationshipbetween grinding temperatures and near surface residual stress and microstructure of theground component. A model of free abrasive machining that predicts statisticalproperties of the load/particle relationship has been developed. The model can be used topredict finished surface roughness. A new effort in the area of form generation incenterless grinding is underway. The use of high pressure fracture to produce smoothdefect free ceramic surfaces is also being pursued.

Additional work in the area of manufacturing processes is directed at modeling ofthe heat treatment process. A commercial finite element package has been adapted topredict the microstructure, deformation, and stress induced by quenching of steelstructures. The model includes the effects of latent heat and volumetric strains inducedby phase changes. Industrial collaborators are providing requisite material properties as afunction of temperature as well as assistance with experimental validation of themodeling.

Fatigue and fracture research includes finite element calculation of residualstresses in railway rails. These residual stresses provide guidelines for the developmentof rail grinding strategies. Additional railway application includes modeling the effect ofroller straightening induced stresses on fast fracture of rail webs. In addition, the failuremode of the mechanical fuse that causes the greatest energy dissipation is being pursued.Finally, boundary element analysis of fracture of smart materials and structures is beingdeveloped.

PublicationsBulsara, V. H., Ahn, Y., Chandrasekar, S., and Farris, T. N., "Polishing and LappingTemperatures," ASME Journal of Tribology, Vol. 119, No. 1, pp. 163-170, 1997.

Ju, Y., and Farris, T. N., "FFT Thermoelastic Solutions for Moving Heat Sources," ASMEJournal of Tribology, Vol. 119, No. 1, pp. 156-162, 1997.

McVeigh, P. A., and Farris, T. N., "Finite Element Analysis of Fretting Stresses," ASMEJournal of Tribology, Vol. 119, No. 4, pp. 797-801, 1997.

Blair, K. B., Krousgrill, C. M., and Farris, T. N., "Harmonic Balance and ContinuationTechniques in the Dynamic Analysis of Duffing's Equation," Journal of Sound andVibration, Vol. 202, No. 5, pp. 717-731, 1997.

Chang, S. H., Balasubramhanya, S., Chandrasekar, S., Farris, T. N., and Hashimoto, F.,"Forces and Specific Energy in Superfinishing of Hardened Steel," Annals of the CIRP,Vol. 46, No. 1, pp. 257-260, 1997.


Beaumont, M., Farris, T. N., and Sun, C. T., "Scratch Testing of Advanced CompositeSurfaces," Composites-Part A: Applied Science and Manufacturing, Vol. 28A, pp. 683-686, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsHucker, S. A., Mann, J. B., Farris, T. N., and Chandrasekar, S., "Thermal Aspects ofGrinding with Superabrasives: Part II," Abrasives Magazine, Dec. 1996/Jan. 1997, pp. 5-7, 28-30.

Harish, G., and Farris, T. N., "Modeling of Skin/Rivet Contact: Application to FrettingFatigue," Proc. 38th AIAA/ASME/ASCE/ASC Structures, Structural Dynamics, andMaterials Conf., pp. 2761-2771, Kissimmee, FL, April 1997.

Farris, T. N., "Thermal Aspects of Grinding," University of Kentucky MechanicalEngineering Colloquium, KY, May 1997.

Mann, J. B., Farris, T. N., and Chandrasekar, S., "A Model for Grinding Burn," Proc. 1st

SAE Aerospace Manufacturing Technology Conf., No. 972247, Seattle, WA, pp. 253-264, June 1997.

Grandt, Jr., A. F., Farris, T. N., and Hillberry, B. M., "Analysis of the Formation andPropagation of Widespread Fatigue Damage," Proc. ICAF: Fatigue in New and AgingAircraft, Ed. P. Poole and R. Cook, Scotland, June 1997.

Harish, G., Szolwinski, M. P., and Farris, T. N., "Finite Element Modeling of RivetInstallation of Riveted Joints for the Prediction of Fretting Crack Nucleation," Proc. 1st

Joint DoD/FAA/NASA Conf. on Aging Aircraft, Ogden, UT, July 1997.

Szolwinski, M. P., Harish, G., Farris, T. N., and Sakagami, T., "An Experimental Studyof Fretting Crack Nucleation in Airframe Alloys: A Life Prediction and MaintenancePerspective," Proc. 1st Joint DoD/FAA/NASA Conf. on Aging Aircraft, Ogden, UT, July1997.

Hill, L. R., and Farris, T. N., "Three-Dimensional Boundary Elements for FlawedPiezoelectric Materials," Proc. 3rd ARO Workshop on Smart Structures, Section 10,Blacksburg, VA, Aug. 1997.

Varney, B. E., and Farris, T. N., "Mechanics of Roller Straightening," Proc. 39th ISSMechanical Working and Steel Processing Conf., Indianapolis, IN, Vol. 55, pp. 111-1121, Oct. 1997.

Szolwinski, M. P., Sakagami, T., Harish, G., and Farris, T. N., "The Use of ThermalImaging for In-Situ Characterization of Frictional Behavior in Mixed-Node FrettingContact," Proc. Symp. on Strength and Fracture of Materials, Tokyo, Japan, Nov. 1997.


Szolwinski, M. P., Harish, G., and Farris, T. N., "Comparison of Fretting Fatigue CrackNucleation Experiments to Multiaxial Fatigue Theory Life Predictions," Proc. IMECESym. on Structural and Aero Mechanical Research in High Cycle Fatigue, Dallas, TX,AD-Vol, 55, pp. 449-457, Nov. 1997.

Madhavan, V., Chandrasekar, S., and Farris, T. N., "Direct Observation of the Chip-ToolInterface in Machining," Proc. IMECE Sym. on Predictable Modeling of Metal Cutting asMeans of Bridging Gap Between Theory and Practice, Dallas, TX, MED-Vol. 6-2, pp.45-52, Nov. 1997.

Sista, P., Swain, S., Chandrasekar, S., and Farris, T. N., "Tool Wear Characteristics ofCBN Tools in the Finish Machining of Tool Steel," Proc. IMECE Sym. on PredictableModeling of Metal Cutting as Means of Bridging Gap between Theory and Practice,Dallas, TX, MED- Vol. 6-2, pp. 161-168, Nov. 1997.

Bulsara, V. H., Ahn, Y., Chandrasekar, S., and Farris, T. N., "Mechanics of Polishing,"Proc. IMECE Sym. on Quality of Traditionally and Nontraditionally Machined Surfaces:Modeling, Analysis and Measurement, Dallas, TX, MED-Vol. 6-1, pp. 225-233,November 1997.

Bulsara, V. H., Chandrasekar, S., and Farris, T. N., "Direct Observation of ContactDamage Produced by Vickers Indentation in Diamond-Like Films," Proc. IMECE Sym.on Dissimilar Material Systems: Manufacturing Processes, Design, and Mechanics,Dallas, TX, MD-Vol. 80, pp. 287-292, Nov. 1997.


ALTEN F. GRANDT, JR.1979

Professor

DegreesB.S., University of Illinois at Urbana-Champaign, General Engineering, 1968M.S., University of Illinois at Urbana-Champaign, Theoretical and Applied

Mechanics, 1969Ph.D., University of Illinois at Urbana-Champaign, Theoretical and Applied

Mechanics, 1971

InterestsDamage-tolerant structures and materialsFatigue and fractureAging aircraftNondestructive inspection

Research AreasBasic research is directed at developing methodology to analyze and design

damage tolerant aerospace structures and materials or to evaluate the remaining safeoperating life of "aging" aircraft. Emphasis is placed on employing both experimentaland numerical approaches to predict the initial growth of preexistent cracks andsubsequent fracture due to cyclic and/or static loads. The influence of corrosion onstructural life is also of interest.

Current research is focusing on problems related to ensuring the structuralintegrity of older aircraft. Deterministic and probabilistic approaches are being employedto determine the influence of widespread fatigue damage on the residual strength andfatigue life of mechanically fastened joints and stiffened panels. Techniques for


quantifying the effect of corrosion on structural integrity are also being investigated,along with assessment of changes in fatigue crack growth properties in structuralmaterials that have experienced extended periods of service.

Other current efforts are examining the nucleation and early growth of fatiguecracks in various materials and structural configurations. In one project, high strengthsteel specimens are subjected to several constant and variable amplitude load histories todetermine the initial growth, coalescence, and fracture of fatigue cracks that develop atnotches in the specimens. In this case crack formation and growth are periodicallyrecorded with a replicating tape that is then examined under a microscope. Anotherrelated project is evaluating the resistance to fatigue crack formation provided by newaluminum alloys, and involves subjecting large, multi-hole specimens to a given numberof fatigue cycles. Those specimens are then sectioned and examined to determine thenumbers and sizes of cracks that have developed at the many hole locations. These datayield statistical crack size distributions that are used to compare the resistance to fatiguecrack formation provided by standard and advanced alloys.

Other recently completed projects have characterized thermal-mechanical fatiguecrack growth in metal matrix composites, analyzed fatigue cracks that originate incomplex rotor-craft components or at dovetail joints in turbine disks, and measured three-dimensional aspects of fatigue crack closure. A technique for monitoring the serviceloading of structural components by the use of pre-cracked coupons mounted to structuralmembers has also been recently studied.

PublicationsElsner, J. H., Kvam, E. P., and Grandt, Jr., A. F., "Microstructure Analysis of FatigueInitiation Life Extension by Reductions in Microporosity," Metallurgical and MaterialsTransactions A, Vol. 28A, pp. 1157-1167, May 1997.

Scheuring, J. N., and Grandt, Jr., A. F., "Mechanical Properties of Aircraft MaterialsSubjected to Long Periods of Service Usage," Journal of Engineering Materials andTechnology, Vol. 119, pp. 380-386, Oct. 1997.

Golinkin, I. A., Ruff, D. D., Kvam, E. P., McCabe, G. P., and Grandt, Jr., A. F.,"Applications of Analysis of Variance (ANOVA) Statistical Methods to Breaking LoadCorrosion Test," Journal of Testing and Evaluation, Vol. 25, No. 6, pp. 565-570, Nov.1997.

Cherry, M. C., Mall, S., Heinimann, M. B., and Grandt, Jr., A. F., "Residual Strength ofUnstiffened Aluminum Panels with Multiple Site Damage," Engineering FractureMechanics, Vol. 57, No. 6, pp. 701-713, 1997.

Grandt, Jr., A. F., "Stress Intensity Factors for Some Through-Cracked Fastener Holes,"Selected Papers on Crack Tip Stress Fields, SEM Classic Papers, Vol. CP2, SPIE


Milestone Series, Vol. MS 138, 1997 (reprint of paper which appeared in 1975 issue ofJournal of Fracture).

Conference Proceedings, Presentations, Invited Lectures and ReportsGrandt, Jr., A. F., and Watkins, W. A., "Teaching Cross-Disciplinary Teamwork Skills toUndergraduate Engineering and Technology Students," Future Directions in EngineeringEducation, Proc. Illinois/Indiana ASEE Section Conference, Indianapolis, IN, pp. 270-275, March 14-15, 1997.

Grandt, Jr., A. F., and Bray, G., "Analyzing the Material Effect in Widespread FatigueDamage," AeroMat '97, 8th Advanced Materials & Processes Conference and Exposition,Williamsburg, VA, May 15, 1997 (abstract only).

Grandt, Jr., A. F., Sexton, D., Golden, P., Bray, G. H., Bucci, R. J., and Kulak, M., "AComparison of 2024-T3 and 2524-T3 Aluminum Alloys under Widespread DamageScenarios," ICAF 97, Fatigue in New and Aging Aircraft," Vol. II, Eds. R. Cook and R.Poole, Proceedings of the 19th ICAF Symposium, International Committee onAeronautical Fatigue, Edinburgh, Scotland, 16-20 June 1997, pp. 659-669.

Grandt, Jr., A. F., Farris, T. N., and Hillberry, B. M., "Analysis of the Formation andPropagation of Widespread Fatigue Damage," ICAF 97, Fatigue in New and AgingAircraft, Vol. I, Eds. R. Cook and P. Poole, Proceedings of the 19th ICAF Symposium,International Committee on Aeronautical Fatigue, Edinburgh, Scotland, 16-20 June 1997,pp. 115-133.

Grandt, Jr., A. F., and Gates, M. D., "Crack Gage Approach to Monitoring FatigueDamage Potential in Aircraft," 1997 Society for Experimental Mechanics SpringConference on Experimental and Applied Mechanics, Bellevue, WA, (2 pages), June 2-4,1997.

Heinimann, M. B., and Grandt, Jr., A. F., "Fatigue Analysis of Stiffened Panels withMultiple Site Damage," presented at 1st Joint DoD/FAA/NASA Conference on AgingAircraft, Ogden, UT, (43 pages), July 8-10, 1997, to appear in Conference Proceedings.

Grandt, Jr., A. F., "Materials Degradation and Fatigue in Aerospace Structures," FinalReport for AFOSR Grant No. F49620-93-0377, Aug. 1997.


C. T. SUN1968

Neil A. Armstrong Distinguished Professorof Aeronautical & Astronautical Engineering

DegreesB.S., National Taiwan University, Taiwan, Civil Engineering, 1962M.S., Northwestern University, Theoretical & Applied Mechanics, 1965Ph.D., Northwestern University, 1967

InterestsCompositesFracture and FatigueStructural DynamicsSmart Materials and Structures

Research AreasMajor research interests include the following areas :

Composite Materials and Structures -- Advanced fiber composites have gained wideapplication in aircraft and aerospace structures. However, our knowledge of thesematerials is still lacking, and a great deal of research is still needed. Our research coversa broad spectrum of mechanics and design of various composite materials and structures.Topics include low velocity impact response and damage analysis, ballistic impact andpenetration of composite structures, design of new hybrid composites for improvedimpact resistance properties, development of theories for laminate failure prediction,inelastic behavior of composites, temperature-dependent properties, modeling of thickcomposite laminates, static and dynamic delamination crack propagation, intelligenttailoring of composite materials and structures and finite element simulation of forming


of thermoplastic composites. Composite systems studies include carbon/epoxycomposites, thermoplastic composites, metal-matrix composites, and ARALL laminates.

The McDonnell Douglas Composite Materials Laboratory is equipped withcomplete testing facilities. In addition, an autoclave and a hot press are available forcomposite specimen fabrication.

Fracture Mechanics -- Fracture mechanics is used to analyze failure in materialsincluding fibrous composites. Behaviors of interfacial cracks between two dissimilarmaterials are of particular interest as they are pertinent to fiber debonding in compositematerials and to delamination in composite laminates. Topics of research includeseparation of fracture modes for interfacial cracks and development of governingequations for dynamic motion of propagating interface cracks. Another major researcheffort concerns fracture criterion utilizing a combination of an extended J-integral forelastic-plastic materials and a crack front plastic work density to predict crack extensionin ductile metals. A new research topic deals with fracture mechanics issues encounteredin using composite materials to repair cracked metal structure in aging aircraft.

Smart Materials and Structures -- The use of piezoceramics as actuators in adaptivestructures demands these materials to perform under increasingly high electric andmechanical loads. Durability and reliability of actuators have become important issues.Our current research aims at solving a number of fundamental problems involving cracksin piezoceramics under combined mechanical and electric loading.

PublicationsVaidya, R. S., and Sun, C. T., "Fracture Criterion for Notched Thin CompositeLaminates," AIAA Journal, Vol. 35, No. 2, pp. 311-316, Feb. 1997.

Tao, J. X., and Sun, C. T., "A Simplified Method for Predicting Onset of Open-ModeFree Edge Delamination," AIAA Journal, Vol. 35, No. 3, pp. 580-582, March 1997.

Potti, S. V., and Sun, C. T., "Prediction of Impact Induced Penetration and Delaminationin Thick Composite Laminates," Int. Journal. Impact Engrg., Vol. 19, No. 1, pp. 31-48,1997.

Lawcock, G., Ye, L., Mai, Y-W., and Sun, C. T., "The Effect of Adhesive BondingBetween Aluminum and Composite Prepreg on the Mechanical Properties of Carbon-Fiber Reinforced Metal Laminates," Composites Science and Technology, Vol. 57, pp.34-35, Jan. 1997.

Chen, J. K., Allahdadi, F. A., and Sun, C. T., "A Quadratic Yield Function for Fiber-Reinforced Composites," Journal of Composite Materials, Vol. 31, No. 8, pp. 788-811,1997.


Sun, C. T., and Qian, W., "The Use of Finite Extension Strain Energy Release Rates inFracture of Interfacial Cracks," International Journal of Solids and Structures," Vol. 34,No. 20, pp. 2595- 2609, 1997.

Qian, W., and Sun, C. T., "Calculation of Intensity Factors for Interlaminar Cracks inComposite Laminates," Composites Science and Technology, Vol. 57, No. 6, pp. 637-650, 1997.

Wang, C., and Sun, C. T., "Experimental Characterization of Constitutive Models forPEEK Thermoplastic Composite at Heating Stage During Forming," Journal ofComposite Materials, Vol. 31, No. 15, pp. 1480-1506, 1997.

McCoy, R. W., and Sun, C. T., "Fluid Structure Interactive Analysis of a Thick-SectionComposite Cylinder Subjected to Blast Loading," Composite Structures, Vol. 37, No. 1,pp. 45-55, 1997.

Beaumont, M., Farris, T. N., and Sun, C. T., "Scratch Testing of Advanced CompositeSurfaces," Composites, Part A: Applied Science and Manufacturing, Vol. 28A, pp. 683-686, 1997.

Wang, C., and Sun, C. T., "Thermoelastic Behavior of PEEK Thermoplastic CompositeDuring Cooling from Forming Temperatures," Journal of Composite Materials, Vol. 31,No. 22, pp. 2230-2248, 1997.

Conference Proceedings, Presentations, Invited Lectures and ReportsSun, C. T., and Jiang, L. Z., "Fatigue Behavior of Piezoelectric Ceramics," in SmartMaterials Technologies (edited by W. C. Simmons, I.. A. Aksay, and D. R. Huston),Proceedings of 1997 SPIE Smart Structures and Materials, San Diego, CA, pp. 129-136,March 1997.

Sun, C. T., "Fracture of Frictional Interfacial Cracks," invited seminar at Univ. ofCalifornia, San Diego, CA, March 4, 1997.

Su, X. M., and Sun, C. T., "3D Singular Stresses in a Cracked Plate," Proceedings of the9th International Conference on Fracture, Sydney, Australia, Vol. 4, pp. 2103-2110, April1-5, 1997.

Sun, C. T., and Guo, C., "Dynamic Delamination in a Polymeric Composite Materials,"(abstract only) presented at the 9th International Conference on Fracture, Sydney,Australia, April 1-5, 1997.

Wu, P. S., and Sun, C. T., "Bearing Failure in Pin Contact of Composite Laminates,"Proceedings of the 38th AIAA/ASME/ASCE/SDM Conference, Kissimmee, FL, April 7-10, 1997.


Sun, C. T., "The Selection of Scale in Modeling Mechanical Behavior of AdvancedMaterials," School of Materials Engineering, Purdue Univ., April 21, 1997.

Sun, C. T., "Three-Dimensional Singular Stresses in a Cracked Plate," Institute ofMechanics, National Taiwan Univ., May 15, 1997.

Sun, C. T., "Recent Developments in Smart Structures and Reliability of SmartMaterials," Pohang Univ. of Science and Technology, presented May 18, 1997, KoreanAdvanced Institute of Science and Technology presented May 29, 1997, and SeoulNational University, May 30, 1997.

Sun, C. T., "Selection of Proper Characteristic Lengths in Modeling CompositeMaterials and Structures," (keynote address), Proceedings of the Korea-Russia JointSeminar on Composite Technology, Changwon, Korea, p. 120-135, May 26-27, 1997.

Sun, C. T., and Qian, W., "A Fracture Criterion for Interfacial Cracks in the Presence ofFriction," presented at the 1997 Joint ASME/ASCE/SES Summer Meeting, NorthwesternUniv., Evanston, IL, June 29-July 2, 1997.

Sun, C. T., Thiruppukuzhi, S. V., and Weeks, C. A., "Characterization of High StrainRate Behavior of Hybrid Composites," presented at the 1997 Joint ASME/ASCE/SESSummer Meeting, Northwestern Univ. Evanston, IL, June 29-July 2, 1997.

Guo, C., and Sun, C. T., "Dynamic Mode II Delamination Crack Propagation inUnidirectional Fiber Composite," presented at the 1997 Joint ASME/ASCE/SES SummerMeeting, Northwestern Univ., Evanston , IL, June 29-July 2, 1997.

Sun, C. T., and Qian, W., "A Proper Treatment of Interfacial Cracks in the Presence ofFriction," Proceedings of the 11th ICCM, Gold Coast, Australia, July 14-18, 1997.

Klug, J., Maley, S., and Sun, C. T., "Characterization of Fracture and Fatigue Behavior ofBonded Composite Repairs," Proceedings of the 1st Joint DoD/FAA/NASA Conferenceon Aging Aircraft, Ogden, UT, July 8-10, 1997.

Sun, C. T., "Characterization and Modeling of Strain Rate-Dependent Behavior inPolymeric Composites," Proceedings of the 18th Risϕ International Symposium onMaterials Science: Polymeric Composites - Expanding the Limits, Eds. S. I. Andersen,P. Bronsted, et al., Roskilde, Denmark, pp. 157-167, September 1997.

Qian, W., and Sun, C. T., "Frictional Interfacial Crack Under Combined Shear andCompressive Loading," Proceedings of the 12th Annual Technical Conference onComposite Materials, American Society for Composite, Dearborn, MI, Oct. 6-8, 1997.

Thiruppukuzhi, S. V., and Sun, C. T., "A Viscoplasticity Model for High Strain RateCharacterization of Polymeric Composites," Proceedings of the 12th Annual Technical


Conference on Composite Materials, American Society for Composites, Dearborn, MI,Oct. 6-8, 1997.

Adams, D. S., and Sun, C. T., "Use of Filament Wound Composites to Exploit LateralConfining Effect in Brittle Materials Subjected to Dynamic Loading," Proceedings of the12th Annual Technical Conference on Composite Materials, American Society forComposites, Dearborn, MI, Oct. 6-8, 1997.

Sun, C. T., "Modeling Rate-Dependent Inelastic Behavior of Polymeric Composites,"Dept. of Mechanical Engrg., Univ. of Notre Dame, Oct. 28, 1997.

Sun, C. T., "Some Unusual Behavior of Composite Laminates," Ford Motors ScienceLaboratory, Dearborn, MI, Oct. 8, 1997.


TERRENCE A. WEISSHAAR1980

Professor

DegreesB.S., (highest distinction), Northwestern University, Mechanical Engineering, 1965S.M., Massachusetts Institute of Technology, Aeronautics & Astronautics, 1966Ph.D., Stanford University, Aeronautics & Astronautics, 1971

InterestsAircraft structural mechanicsAeroelasticityIntegrated Design

Research AreasPrimary research areas include optimization of structural concepts for smart

aeroelastic structures and efficient multidisciplinary design. Currently, two primaryareas are of interest:

• Aeroelastic tailoring and active flexible wings. This includes using conventionalarticulated surfaces such as ailerons and leading edge devices for roll control, aswell as using smart materials to change the camber of advanced wing concepts foraircraft control. Objectives also include aeroelastic design for reduced drag andoptimization of smart wing flutter suppression systems for micro-air vehicles. Weare also developing innovative techniques with advanced composite structuredesign to find optimal designs and reduce time to develop new concepts.


• Design methodology. - developing new methods and algorithms to improve theability of a design team to generate innovative, creative concepts for aerospacevehicles. This includes examining how the external aerodynamic and internalstructural topology of lifting surfaces can be addressed simultaneously in thedesign process. This also includes introducing manufacturing concerns anddecisions early in the design process and creating, through the early use of finiteelement models, more feed-forward/feed-back paths.

We have been examining how to use new modeling software to generate andpresent accurate, useful information to designers by displaying load paths andtheoretically optimal designs. This leads to an improved conceptual design process forairplane structures that begins with a few participants and quickly proceeds to a high levelwith diverse technical groups represented. We are involved in the creation of anobject-oriented system, using Adaptive Modeling Language (AML), to provide anatural, integrated, virtual environment for modeling, linking and simulating theaircraft design process from its earliest conceptual phase into preliminary design.When completed, this system will allow an integrated product team access to avirtual environment that scientifically simulates the iterative, collaborative processrequired to design an airplane in a short amount of time.

Conference Proceedings, Presentations, Invited Lectures and ReportsWeisshaar, T.A., “UAV Design Issues,” DARPA/Defense Research Science Council,Arlington, Virginia, January 1997.

Leeks, T.J. and Weisshaar, “Discrete Grid Actuator Stiffened Panels for AeroelasticUse,” Proceedings of the SPIE Smart Structures Conference, San Diego, Calif., March1997.

Weisshaar, T.A. “Aircraft Aeroelasticity-Design Impact and Issues,” Naval AviationExecutive Institute, Patuxent River Naval Research Center, Maryland, October 1997.

Weisshaar, T.A. “Aeroelastic Tailoring of High Performance Lifting Surfaces,” Seminar,University of Illinois, Aerospace Engineering Dept.., October 1997.

Weisshaar, T.A., Komarov, V. A., “Integrated Air Vehicle Structural Design for the FullLife Cycle,” Air Vehicles Directorate, U. S. Air Force Research Laboratory, Wright-Patterson AFB, Ohio, December 9, 1997

“Report on United States Air Force Expeditionary Forces,” SAB-TR-97-01 (3 volumes),February 1998. (This study was commissioned by the Secretary of the Air Force andChief of Staff to develop a concept for Air Expeditionary Forces. Professor Weisshaarcontributed, with other panel members, to the new technology thrusts portion of thisreport).


ACTIVE RESEARCH PROJECTSJULY 1, 1997 to JUNE 30, 1998


RESEARCH AND OTHER SCHOLARLY ACTIVITIES

The 1997-98 academic year realized $3,379,517 of externally funded research. Adetailed listing of all outside sponsored research projects that were active during theperiod July 1, 1997 to June 30, 1998 is given in the Active Research Projects section.Please note that students and faculty are involved in many other research efforts whichare not sponsored by external funds. The externally funded research for the 1997-98 yearwas obtained from the following sources.

SOURCE OF SPONSORED RESEARCH FOR 1997-1998Source Percentage of Total

Department of Defense 48%NASA 22%National Science Foundation 13%Industrial 9%

Other 8%Total 100.0%


SPONSORED RESEARCH PROJECTSACTIVE DURING THE PERIOD JULY 1, 1997 TO JUNE 30, 1998

SPONSOR PROJECT TITLE PROJECTPERIOD

AWARDAMOUNT

P. I.

NASA Indiana Space Grant Consortium Program Grant 03/01/91-09/30/97

$1,045,812 Andrisani

NASA A Proposal to Establish the NASA Academy inAeronautics

01/01/97-12/31/97

$42,734 Andrisani

NASA National Space Grant College and FellowshipProgram

03/01/97-02/28/01

$333,125 Andrisani

IBM Numerical Simulation of Turbulent AxialVortices Using an IBM SP2 Parallel Computer

07/01/96-06/30/98

$24,574 Blaisdell

NASA High Reynolds Number Experiments on BypassDuct and Strut Flows

07/14/95-10/31/98

$288,441 CollicottCo-P.I:Sullivan

NSF Career: Experimental Investigation of theInternal Structures in Atomizing Orifice Flows

08/01/95-07/31/99

$284,978 Collicott

UnitedTechnologies

United Technologies/Pratt & Whitney 04/01/95-12/31/75

$18,000 Collicott

CumminsEngine

NSF Matching 01/01/97-12/31/99

$30,000 Collicott

Allied Signal Special Progams 05/01/98-12/31/75

$2,800 Collicott

NASA Indiana Space Grant Consortium 03/01/91-06/30/97

$2,280 Collicott

NSF A Proposal to Establish an Engineering ResearchCenter for Collaborative Manufacturing

10/1/94-08/30/98

$17,141 Corless

Boeing Adaptive Control of Milling Machines: StabilityAnalysis

04/01/98-03/31/99

$49,000 Corless


10/1/9709/30/98

$19,954 Crossley

NASA Indiana Space Grant 03/01/91-6/30/97

$4,452 Crossley

AerospaceCorp.

Genetic Algorithms 06/01/97-08/31/97

$3,000 Crossley

NASA Topology Design of Rotor Blades forAerodynamic and Structural Consideration

07/01/97-06/30/98

$22,000 Crossley

NASA Application of the Spectral Element Method toInterior Noise Problems

08/11/95-06/30/98

$52,027 Doyle

ONR An Experimental Computational Investigation ofInelasticity in Nanostructured and LayeredMaterials

06/01/97-05/30/00

$257,000 Espinosa

NSF Tribo-Mechanics of Nanostructured Materials 07/01/96-12/31/99

$220,000 Espinosa

NSF Effect of Grain Size, Second Phases and Texturein the Dynamic Failure of Ceramics

09/15/95-08/31/99

$148,790 Espinosa

AFOSR An Investigation on High Temperature Behaviorof Laminate and Nanostructured CompositeMaterials

10/15/97-10/14/98

$97,778 Espinosa



AWARDAMOUNT

P. I.

AFOSR Instrumentation for Full Field Measurement withNanosecond Resolution

04/01/97-12/31/98

$237,288 Espinosa

ARO National Defense Science & Engrg.Graduate Fellow

08/1/94 -08/31/98

$96,540 Farris


10/01/94-09/30/98

$424,457 Farris

GE AircraftEngines

Fretting Fatigue Feature Testing 03/15/97-12/14/98

$75,394 Farris

NSF Use of Polishing Process Model as an Examplefor Manufacturing System Design

09/15/97-06/30/00

$194,801 Chandrasekar(Co-P.I.Farris,Compton)

Univ. Dayton Res. Inst.

Fretting Fatigue of Flat, Titanium Surfaces 03/01/98-04/30/99

$193,000 Farris(Co-P.I.Grandt)

GE AircraftEngines

Titanium Fretting Fatigue Life Modeling 03/15/98-12/15/98

$30,000 Farris

GE AircraftEngines

Forward Outer Seal/Rabbet Edge-of-ContactTesting

06/01/98-12/31/98

$74,675 Farris

Cummins Mapping of a Residual Stress 10/01/97-09/30/98

$41,387 Farris

Caterpillar Process Performance Model for Hard Turning 01/15/97-01/14/98

$90,400 Chandrasekar(Co-P.I:Farris)

NASA New H2 / H∞ Control Synthesis for the F-18 07/01/95-07/31/98

$66,000 Frazho

ALCOA Validation of Widespread Fatigue DamageModels

07/01/96-06/30/98

$59,196 Grandt

AFOSR Analysis of Widespread Fatigue Damage inAircraft Structures

02/15/98-11/30/98

$210,000 Grandt(Farris,Hillberry,Co-P.I.'s)

LockheedMartin

Crack Coalescence Analysis MethodsDevelopment

01/01/97-12/31/98

$66,947 Grandt

AFOSR Modeling Primary Atomization Processes 07/01/96-11/30-98

$211,853 Heister

IBM Nonlinear Modeling of Droplet AtomizationProcesses

08/01/96-7/31/98

$25,000 Heister

ARO Modeling Diesel Engine Injector Flows 05/20/98-02/14/99

$45,000 Heister

Allied-Signal Special Program 05/01/98-12/31/75

$1,000 Heister

NASA Indiana Space Grant Consortium Program Grant 03/01/92-06/30/97

$4,022 Heister

NASA Trajectory Design Strategies for Libration PointMissions that Incorporate Invariant Manifolds

08/01/96-07/31/98

$44,000 Howell

NASA Application of Dynamical Systems Theory to theDesign and Development of SpacecraftTrajectories

08/19/96-08/19/98

$125,000 Howell



AWARDAMOUNT

P. I.

JPL Analysis of Transfer Trajectories fromEarth to Sun-Earth L2 Lissajous Orbits

050/1/95-07/31/98

$154,445 Howell

JPL Saturn Gravity Field Modeling Accuracy 06/01/96-01/09/98

$40,000 Longuski

NASA Theory of Maneuvers for Small AutonomousSpacecraft

08/19/96-09/30/97

$22,000 Longuski

NASA Indiana Space Grant 03/01/91-06/30/97

$4,049 Longuski

JPL/NASA Mission Design Challenges for the Outer PlanetsProgram

06/25/97-08/31/97

$4,929 Longuski

JPL/NASA Low-Thrust and Gravity-Assist TrajectoryDesign for Planetary Missions

11/03/97-12/31/99

$50,000 Longuski

NASA The Use of Kirchhoff's Method in JetAeroacoustics

12/15/94-07/14/97

$84,400 Lyrintzis

ARO An Extended Kirchhoff Method for RotorcraftImpulsive Noise

03/01/97-08/31/97

$20,000 Lyrintzis

NASA A Study of Rotorcraft Blade-tip Shape NoiseCharacteristics

01/15/97-08/31/97

$25,000 Lyrintzis

NASA On the Development of Supersonic Jet NoisePrediction Methodology

11/25/97-11/24/98

$33,391 Lyrintzis

NSF National Science FoundationYoung Investigator Award

10/01/93-09/30/98

$257,500 Rotea

UnitedTechnologies

Industrial Match to NSF Young InvestigatorAward

11/01/96-07/01/98

$20,000 Rotea

AFOSR Laminar-Turbulent Transition in HypersonicBoundary Layers: Development of a High-Reynolds Number Mach-6 Quiet-Flow Testing

03/01/98-02/28/99

$206,600 Schneider

Lockheed Unsteady-Response Testing of Kulite PressureTransducers Using Weak Shock Waves

06/01/97-12/31/97

$5,000 Schneider

AFOSR Laminar-Turbulent Transition in High-SpeedCompressible Boundary Layers: Continuation ofElliptic-Cone Research

11/15/96-11/14/98

$249,378 SchneiderCo-P.I.:Collicott

NASA High-Lift Aerodynamics 06/01/93-08/31/97

$179,783 SullivanCo-P.I.:Schneider

NASA Boundary-layer Transition Detection inCryogenic Wind Tunnel using Fluorescent Paints

01/23/96-01/31/99

$150,000 Sullivan

NASA Pressure and Temperature Measurement ofRotating Machinery using Fluorescent Paints

04/16/96-06/30/98

$150,000 Sullivan

NASA Pressure and Temperature Sensitive PaintMeasurements on Rotors

05/01/97-04/30/99

$40,000 Sullivan

Select Tech Pressure Sensitive Paint for Low SpeedApplication

11/15/97-12/31/97

$6,000 Sullivan

Boeing Pressure and Temperature Paint Laser ScanningSystem

05/01/97-07/17/98

$65,000 Sullivan



AWARDAMOUNT

P. I.

ARO Lightweight Layered Materials/Structures forDamage Tolerant Armor

09/01/96-11/30/98

$1,489,625 Sun(Co-P.I.’s:Doyle,Espinosa)

ONR Dynamic Constitutive and Failure Modeling ofComposite Materials and Structures

02/01/96-09/30/98

$354,720 Sun

Univ.California

Testing and Modeling of Strain-Rate DependentConstitutive Properties of Composite Fan Blade

10/01/96-09/30/97

$30,000 Sun

ONR Development of Lightweight Multi-CoreComposite Structures for Surface Ship HullApplications

06/01/97-12/31/99

$163,214 Sun

McDonnellDouglas

Viscoplastic Modeling for HSCT CandidateComposite Materials

06/15/95-06/14/97

$103,214 Sun

Army Development of Novel Multi-LayeredComposite Structures for Ballistic Impact

07/01/94-12/31/97

$84,724 Sun

TuskegeeUniv./NSF

Interlaminar and Compressive Properties ofComposites - A Subcontract to Tuskegee Univ.for the Establishment of a Center for InnovativeManufacturing of High Performance CompositeMaterials

09/01/97-08/3198

$40,000 Sun

AFOSR Characterizing and Modeling Physical Aging inPolymeric Composites

12/0197-11/30/98

$94,000 Sun

AFOSR Modeling and Lowering Residual Stresses inBonded Composite Patch Repairs of MetallicAircraft Structures

02/01/98-10/31/98

$75,000 Sun

Applied Res.Assoc.

Preparation of Composite Specimens 08/01/97-12/31/97

$7,296 Sun

AFOSR Advanced Aircraft Structural Design 09/15/97-01-15/98

$2,500 Weisshaar

Techosoft Air Vehicle Modeling and Structural Simulation 07/28/97-05/31/98

$36,200 Weisshaar

McDonnellDouglas

Investigate the Active Flexible Wing Concept forDesign of Light-Weight Advanced ConceptStructures

06/01/97-12/15/97

$29,939 Weisshaar


GRADUATE THESESJULY 1997- JUNE 1998


MASTER’S THESES

Student/Major Professor

Thesis Title DegreeDate Granted

Bougher, JeffreyT. N. Farris

"Part Deflection in Precision Turning ofHardened Steels"

M. S.May 1998

Fanjoy, David W.W. A. Crossley

“Using the Genetic Algorithm forMultidisciplinary Helicopter Rotor AirfoilDesign: Shape and Topology Approaches"

M. S.May 1998

Golden, Patrick J.A. F. Grandt, Jr.

"A Comparison of Fatigue Crack Initiationat Holes in 2024-T3 and 2524-T3Aluminum Alloys"

M. S.December 1997

Henry, Mark E.S. H. Collicott

"An Experimental Investigation of aCavitating Slot Orifice"

M. S.August 1997

Nuss, Jason S.K. C. Howell

"The Use of Solar Sails in the CircularRestricted Problem of Three Bodies"

M. S.May 1998

Pakalapati, RajeevT. N. Farris

"Simulation of Heat Treatment of Steels:Experimental Verification of Distortion Dueto Martensitic Transformations"

M. S.August 1997

Ross, Tamaira E.W. A. Crossley

"Designing for Minimum Cost: A Methodto Assess Commercial AircraftTechnologies"

M. S.May 1998

Sexton, Darren G.A. F. Grandt, Jr.

"A Comparison of the Fatigue DamageResistance and Residual Strength of 2024-T3 and 2424-T3 Panels Containing MultipleSite Damage"

M. S.August 1997

Torgerson, Shad D.J. P. Sullivan

"Pressure Sensitive Paints for AerodynamicApplications"

M. S.August 1997

Witte, Gerhard R.J. P. Sullivan

"Experimental Investigation of a 40% ThickHalf-Span Boundary Layer Control Wing"

M. S.May 1998


DOCTORAL THESES

Student/Major Professor

Thesis Title DegreeDate Granted

Brockman, Mark L.M. J. Corless

"Quadratic Boundedness of UncertainNonlinear Dynamic Systems"

Ph.D.December 1997

Guo, ChengC. T. Sun

"Dynamic Delamination of Composites" Ph.D.August 1997

Hill, Lisa R.T. N. Farris

"Three-Dimensional Piezoelectric BoundaryElements"

Ph.D.August 1997

Hoffenberg, R.J. P. Sullivan

"Simulation of High-Lift Wake Behavior" Ph.D.December 1997

Jiang, LongzhiC. T. Sun

"Fracture and Fatigue Behavior ofPiezoelectric Materials"

Ph.D.May 1998

Klug, JohnC. T. Sun

"Efficient Modeling of PostbucklingDelamination Growth in CompositeLaminates using Plate Elements"

Ph.D.August 1997

Lu, JianboR. E. Skelton

"Robust Control and Control SystemIntegration Using Finite-Signal-to-NoiseModel"

Ph.D.December 1997

Schmisseur, John D.S. P. Schneider

"Receptivity of the Boundary Layer on aMach-4 Elliptic Cone to Laser-GeneratedLocalized Freestream Perturbations"

Ph.D.December 1997

Shi, GuojunR. E. Skelton

"Integrated Identification, Modeling andControl with Applications"

Ph.D.December 1997

Smith, Monty J.A. E. Frazho

"Multiple Objective Control SystemSynthesis via Lifting Techniques"

Ph.D.December 1997

Thiruppukuzhi, SrikanthC. T. Sun

"High Strain Rate Characterization andModeling of Polymer Composites"

Ph.D.December 1997

Tragesser, Steven G.J. M. Longuski

"Analysis and Design of AerobrakingTethers"

Ph.D.December 1997

Wernimont, Eric J.S. D. Heister

"Experimental Study of Combustion inHydrogen Peroxide Hybrid Rockets"

Ph.D.August 1997


Zhu, ChangmingC. T. Sun

"Constitutive Modeling of PolymericComposites Under Various LoadingConditions"

Ph.D.December 1997


Colloquium Series1997 - 1998


Colloquium Series - Fall 1997

DATE/TIME TOPIC SPEAKER

*September 18, 1997 Rediscover Aluminum: New Dr. J. T. StaleyTechnology for Affordable Alcoa Technical CenterAerospace Systems

October 7, 1997 Reducing Cycle Time and Dr. David L. GroseCost in Product Development Boeing Commercial Airplane

Groupand Preliminary Design

October 16, 1997 Soft Computing and Artificial Mr. Mark E. Dreier. Intelligence in the Aerospace Bell Helicopter Textron, Inc.

Industry

October 23, 1997 Creative Research - Collaboration Dr. Michael J. SalkindSuccess in a Changing World President, Ohio Aerospace Inst.Optimizing the Economics Manager, Propulsion andof Space Combustion Center

TRW Space & Electronics

November 13, 1997 Linear and Nonlinear Wave Dr. T. W. WrightPropagation in Dispersive Army Research LaboratoryMaterials

November 20, 1997 Aircraft Engine Materials: Recent Dr. James WilliamsTrends and Future Directions General Electric (GSAE)

*Midwest Mechanics Seminar, sponsored jointly by the Schools of Aeronautics andAstronautics and Mechanical Engineering


Colloquium Series - Spring 1998

DATE/TIME TOPIC SPEAKERJanuary 22, 1998 Helicopter Rotor Noise Dr. Kenneth S. Brentner

Prediction: Background, Current NASA Langley Research CenterStatus and Future Direction Hampton, VA

February 12, 1998 The Airborne Laser: A Dr. Steven LambersonRevolutionary Weapon System M. I. T. Lincoln Laboratory

Kirtland AFB, New Mexico

February 25, 1998 Team-Based, Project-Oriented Prof. Stephen BatillCapstone Design Experiences Univ. of Notre Damein Engineering Notre Dame, IN

February 26, 1998 Aerospace Multidisciplinary Dr. Vipperla B. VenkayyaDesign Optimization U. S. Air Force Res. Lab.

Wright-Patterson AFB, OH

March 5, 1998 Cohesive Zone Parameters Dr. Sunil Saigaland Energy Dissipation in Program Dir. for the Mech. &Soft Adhesives with Cohesive Materials AreaElements in Viscoelastic National Science FoundationFracture

*March 6, 1998 The Reverse Turbulent Cascade Prof. Philip S. Marcusand it's Consequences in Lab. Univ. of California at Berkeleyand Astrophysical Flows Berkeley, CA

March 26, 1998 The Future of Composites in Mr. C. R. SaffAerospace Structures The Boeing Company

St. Louis, MO

April 2, 1998 Electric Propulsion: The Ms. Mary KriebelPropulsion of the Future TRW Space & Elect. GroupWho's Time has Come

*April 24, 1998 Genesis and Control of Coherent Prof. Fazle HussainStructures in Near-Wall Univ. of HoustonTurbulence

*Midwest Mechanics Seminar, jointly hosted by the School of Aeronautics & Astronautics and the Mechanical Engineering Department

**Jointly hosted seminar by the School of Aeronautics & Astronautics and the Student Chapter of theAmerican Helicopter Society


HIGHLIGHTS OF FACULTY ACCOMPLISHMENTS

•Professor Dominick Andrisani served as the dean of the NASA Academy at DrydenFlight Research Center in Edwards, California.

•Professor Gregory Blaisdell was the first recipient of the W. A. Gustafson TeachingAward.

•Professor Steven Collicott spent the Spring semester on sabbatical at Lockheed Martin,California.

•Professor James F. Doyle, authored the 2nd edition of the book, Wave Propagation inStructures.

•Professor Horacio Espinosa was awarded the Office of Naval Research YoungInvestigator Award.

•Professor Arthur Frazho co-authored the book, Constrained Interpolation, CommutantLifting and Systems.

•Professor W. A. Gustafson was awarded the Dean M. Beverly Stone Award and theElmer F. Bruhn Teaching Award.

•Professor Kathleen Howell spent the Spring semester on sabbatical working for the JetPropulsion Lab, California, and with NASA Goddard.

•Professor Anastasios Lyrintzis spent the 1997-1998 academic year at the ComputerScience Department at Purdue as part of the Program of Study in a Second Discipline.Also, he spent the summer at Boeing as part of the Welliver Fellowship Program.

•Professor Mario Rotea spent the Fall and Spring semesters working for UnitedTechnologies Corporation, Connecticut.

•Professor C.T. Sun was awarded the 1998 Medal of Excellence in Composite Materialsby the University of Delaware Center for Composite Materials and completed his booktitled, Mechanics of Aircraft Structures.


STUDENT ACHIEVEMENT HIGHLIGHTS

Kerrie Benish was honored by Sigma Gamma Tau, an aerospace honorarysociety, as the Outstanding Senior for 1998 as well as selected as one of six students toreceive the award from the National Sigma Gamma Tau Society. Miss Benish alsoreceived the Herbert F. Rogers Scholarship.

The Magoon Teaching Assistant Awards were awarded to Daniel Bodony, JasonBowman, Eric Campbell, Evangelos Koutsavdis, and Belinda Marchand. SophomoreCasey Kirchner and Tyson Strutzenberg, Juniors Dan Javorsek and Nicole Key, andSeniors Lisa Brilliant and Kevin Dressel received the William Koerner Scholarships.

Abigail Dobbins and Philip Schneider were named the Elmer F. BruhnUndergraduate Research Assistantship winners.

American Helicopter Society (AHS)The Purdue Chapter of the American Helicopter Society, dedicated to promoting

and advancing student involvement within the rotorcraft industry, completed its third yearas a student organization. Professor William Crossley is the advisor for AHS.

American Institute of Aeronautics & Astronautics (AIAA)The Purdue Chapter of the American Institute of Aeronautics and Astronautics

was led this year by: President Greg Roth. Professor Marc Williams serves as theadvisor.

Sigma Gamma TauSigma Gamma Tau, the aerospace engineering honor society, has 65 members

and Justin Hemann served as chapter president, and Professor Martin Corless is thechapter advisor.

Students for Exploration and Development of Space (SEDS)SEDS members are dedicated to promoting the exploration and development of

space by educating people about the benefits of space. SEDS coordinated the secondannual Fall Space Day, an educational event for children in grades three through eight.More than 250 students and teachers attended the event, and Greg Harbaugh, '78 was thefeatured astronaut. Additional educational outreach activities include an open forumdiscussion entitled "Astronauts or Astrobots?" with Dr. Friedman and Dr. Zubrin, andparticipation in the KC-135 "Vomit Comet" experiment. Professor James Longuski isthe chapter advisor.

American Society for Testing and Materials (ASTM)The Purdue ASTM Student Chapter was founded in the Fall of 1996 by an

interdisciplinary group of graduate students involved primarily in fatigue and fractureresearch. The goal of the organization is to promote the exchange of information and


expertise in the areas of materials research and testing on the Purdue campus. ProfessorsA. F. Grandt, Jr. and B. M. Hillberry (School of Mechanical Engineering) are theChapter Advisors.


ALUMNI HIGHLIGHTS

Distinguished Alumnus

Alumnus John Hayhurst, BS '69, was awarded an honorary doctorate degree. Dr.Hayhurst is Vice President for the Americas, for the Boeing Corporation.

Roy Bridges, MS '66, received the Distinguished Engineering Alumnus award.Mr. Bridges is the Director of the Kennedy Space Center and a retired member of theAstronaut Corp.

Astronaut Alumni

Mark Lewis Polansky, BS '78, MS '78, completed astronaut training, which makeshim the 21st Purdue University alumnus and the 14th School of Aeronautics andAstronautics alumnus to join the astronaut fleet.

Alumni Receptions

Alumni receptions this year were held in California, Indiana, and Texas.Additionally, “Breakfast with the Professors” receptions were held during Homecomingand Gala Weekend this year. We continued with our “Welcome New Alumni,”receptions, which we began last year, held immediately after graduation for our newestalumni.


CURRICULUM & COURSE OFFERINGS


190-Introduction to Aerospace EngineeringMath Chemistry Physics Communications Economics Liberal Arts

Thermodynamics Electrical Circuits Computer Skills/Programming

251-Introduction to Aerospace DesignAerodynamics Dynamics and Control Propulsion Structures and Materials

Required Undergraduate333-Fluid Mechanics & Lab. 203-Aeromech.I(statics/dyn) 372-Jet Propulsion 204-Aeromech. II (Str of Mat.)334-Aerodynamics and Lab 340-Dynamics and Vibrations 352-Structural Analysis & Lab

464-Control System Analysis421-Flight Dynamics & Lab

Undergraduate Electives412-Intro to CFD 361-Intro to Random Variables 439-Rocket Propulsion 453-Matrix Methods in Struct.414-Compressible Aero416-Viscous Flows

474-Exp. Flight Mechs.

Design Electives490a-Aerodynamic Design 490r-Control Design 490p Propulsion Design 490d-Structure Design

451-Capstone Design (Aircraft or Spacecraft)

Undergraduate/ Graduate Electives511-Intro. to Fluid Mech. 507-Basic Mechanics 538-Air Breathing Propulsion 547-Experimental Stress Anal.512-Computational Aero 508-Optimization in Aero. Eng. 539-Adv. Rocket Propulsion 553-Elasticity in Aero. Eng513-Transonic Aero 531-Flight Mechanics 537p-Hypersonic Propulsion 554-Fatigue in Struct. and Mat.515-V/STOL Vehicles 532-Orbit Mechanics 590m-Aerospace Combustion 555-Mech. of Composite Mat.517-Unsteady Aerodynamics 540-Spacecraft Attitude Dyn. 556-Aeroelasticity519-Satellite Aerodynamics 564-Systems Anal. and Control 557-Inelastic Behavior of Mat.520-Experimental Aero. 565-Guidance and Control 558-Finite Element Methods590b-Aeroacoustics 567-Intro to Stochastic Proc. 559-Mech. of Friction & Wear590c-Low Gravity Fluid Mech. 574-Digital Flight Control Sys. 590a-Struct. Dyn and Stability590s-Tech. Fluid Mech. 630-Stability of Free Surfaces 590n-NDE of Struct and Mat.

Graduate Electives 603 Theoretical Methods611 Principles of Fluid Mech. 607-Var.Prin. of Mechancis 646 Elastic Wave Propagation613 Viscous Flow Theory 664 Uncertain DynSystems 690d - Adv. Orbit Dynamics 652 Theory of Plates&Shells626 Math. Theory Turbulence 660-Operator Methods 690e- Optimal Trajectories 654 Fracture Mech.690t Lam-Turb Transition 666-Nonlinear Dyn,Sys,Control 690g-Astro.Nav.&Guidance 655 Composite Mat.&Struct.

684-Design of Dyn.Systems. 690r-Multi.Feedback Control

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