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Project: PS 4.1. Modeling of Rotorcraft Noise in Maneuvering Flight. PI: Kenneth S. Brentner (814)865-6433, [email protected] Graduate Students: Hsuan-Nien Chen (started Dec 2002 – PhD) 2005 RCOE Program Review May 3, 2005. Kenneth S. Brentner, Dept. of Aerospace Engineering. - PowerPoint PPT Presentation
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PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 1
Modeling of Rotorcraft Noise in Modeling of Rotorcraft Noise in Maneuvering FlightManeuvering Flight
PI: PI: Kenneth S. Brentner (814)865-6433, Kenneth S. Brentner (814)865-6433, [email protected]@psu.edu
Graduate Students: Graduate Students:
Hsuan-Nien Chen (started Dec 2002 – PhD)Hsuan-Nien Chen (started Dec 2002 – PhD)
2005 RCOE Program Review2005 RCOE Program Review
May 3, 2005May 3, 2005
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering
Project: PS 4.1
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 2
Overview of Work
Project Overview (Ken Brentner) Acoustic Analysis (Sam Chen) Summary (Ken Brentner)
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 3
Background/Problem Statement:
Current rotor aerodynamics and noise prediction primarily for steady flight conditions
Noise of maneuvering rotorcraft can be significantly higher than for a similar steady flight condition
A tool is needed that is able to predict noise generated by rotorcraft in maneuver — including the transient aircraft motion and blade loading.
Technical Barriers or Physical Mechanisms to Solve: Acoustics
Very complex source motion and time dependence Complicated time-dependent noise directivity Transient blade loading and motion are an “additional” noise source
Aeromechanics Nonperiodic blade loading and motion is unique to each blade Rotor-wake interaction extremely challenging problem
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 4
Task Objectives:
Develop a noise prediction capability for rotors in steady AND transient maneuvers (including multiple rotors)
Gain better understanding of noise directivity in maneuvering flight—especially the components (thickness, loading, transients, etc.) of maneuver noise
Quantify the importance of transients
Assess the requirements for wake fidelity and airloads accuracy in the context of maneuver noise-prediction
Improve maneuver noise prediction through the utilization and/or development of maneuvering wake
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 5
Approach:
Develop acoustics code with full rotor-blade motion and complete aircraft motion
Utilize best available comprehensive analysis tools for initial developmental work, accepting known weaknesses
Incorporate advanced maneuver airloads/wake modeling as it becomes available
Emphasis is on approaching the problem from the acoustics point of view, then working to provide required input data
Expected Research Results or Products: A new rotorcraft noise prediction code—much more useful
and general purpose than the current generation of codes Understanding of the extra noise generated in maneuvers Guidance for the development of maneuver aerodynamics
and flight dynamics (acoustic requirements)
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 6
Overview of Work
Project Overview Acoustic Analysis Summary
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 7
Maneuver Noise Analyzed
Several maneuvers were analyzed: Arrested descent Left turn entry (with three different roll rates) Right turn entry (with three different roll rates) Left-right-left roll reversal maneuver Right-left-right roll reversal maneuver Quick stop maneuver Level acceleration maneuver Climb maneuver
Focus of this presentation on maneuvers with roll motion
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 8
Code Validation – BVI Condition
Compared predictions with DNW acoustic measurement Contemporary design 4-bladed rotor for utility helicopter μ = 0.2 and CT=0.0056 and zero shaft tilt angle (wind tunnel conditions
not fully reported) Two mic positions, Mic 9: Ψ=150º and 25º below; Mic 7: Ψ=150º in-plane.
Aerodynamic calculation was performed by RCAS free vortex-wake model
Mic 7 Mic 9
Predicted levels lowered by 20 Pa for clarity
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 9
Transient Maneuver Noise Identified
OA
SP
L-T
hic
kness
(dB
)
Roto
rN
orm
alF
orc
eR
atio
50
60
70
80
0.7
0.9
1.1
1.3
Time (sec)
OA
SP
L-Loadin
g(d
B)
Roto
rN
orm
alF
orc
eR
atio
0 20 40 60 8060
75
90
0.7
0.9
1.1
1.3
Rotor Normal Force Ratio*
OASPL (dB)
Observer Location : (800, - 400, 0) m
* Rotor Normal Force / Gross Weight
Fixed Observer Location
Observer Location: 30R form rotor hub, 45º below rotor and 120º azimuth angle
Moving Observer Location
65
70
75
80
85Thickness Noise
Time (sec)
0 20 40 60 8080
85
90
95Total Noise
65
70
75
80
85Thickness Noise
Time (sec)
0 20 40 60 8080
85
90
95Total Noise
Time (sec)0 20 40 60 80
75
80
85
90
95
OA
SP
L(d
B)
Loading Noise
65
70
75
80
85Thickness Noise
Time (sec)
0 20 40 60 8080
85
90
95Total Noise
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 10
Turn-Entry Maneuvering Flight
Both right and left turn-entry maneuvering flights.
Three different turn transient duration settings: 0.5, 1 and 5 seconds.
Focus on the helicopter roll maneuver. Left Turn
Right Turn
0.5 sec duration
1 sec duration
5 sec duration
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 11
OASPL “spike” amplitude is a strong function of transient duration
OA
SP
L-
Th
ickn
ess
(dB
,re
f2
0P
a)
70
75
80
85
Retreating Side
Time (sec)
OA
SP
L-
Lo
ad
ing
(dB
,re
f2
0P
a)
0 2 4 6 8 1080
85
90
95
0.5 sec duration
1 sec duration
5 sec duration
Observer locations: 45º below rotor tip path plane 30 R from rotor hub Upstream ±60º from centerline
OA
SP
L-
Th
ickn
ess
(dB
,re
f2
0P
a)
65
70
75
80
Advancing Side
Time (sec)
OA
SP
L-
Lo
ad
ing
(dB
,re
f2
0P
a)
0 2 4 6 8 1075
80
85
90
95
Acoustic Signature with Different Roll Rates
Thickness noise
Loading noise
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 12
Disk Loading in Right Turn-Entry Maneuver
0.5s duration 1.0s duration 5.0s duration
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 13
Rotor Wake Geometry for Right Turn
Wake bundling effect starts from Rev 27
Interaction of wake bundle and blade result in a “Super BVI” occurs in both Revs 28 and 29
Helicopter roll overshoot during maneuver is partially responsible
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 14
BVISPL Prediction in Right Turn-Entry Maneuver
1.0s duration0.5s duration 5.0s duration
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 15
Disk Loading in Left Turn-Entry Maneuver
0.5s duration 1.0s duration 5.0s duration
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 16
Rotor Wake Geometry for Left Turn
The wake bundling effect observed in the retreating side.
The wake bundling effect also occurred in the advancing side but less interaction with rotor blades.
The strength of the “super BVI” is less than what we observe in the right turn.
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 17
BVISPL Prediction in Left Turn-Entry Maneuver
0.5s duration 1.0s duration 5.0s duration
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 18
Summary for Turn Maneuvers
Both right and left turns experienced vortex bundling in the transient maneuver condition. Right turn maneuver has stronger bundling and interaction in the aggressive turn.
The overshoot in roll attitude results in strong BVI during the right turn maneuver. It is like a mini roll-reversal maneuver.
A more aggressive maneuver triggers a stronger wake bundling condition. As this bundled tip vortices encounter the rotor during the maneuver has the potential to generate very high level of impulsive loading and BVI noise.
Right turn maneuver generated higher noise level than the left turn.
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 19
A More Complex Example:LRL Roll Reversal Maneuver
The LRL roll reversal maneuver consists of three components within 6 sec:
A -50º left roll over approximately 2 sec.
A 100º right roll over approximately 2 sec.
A second left to zero roll angle over approximately 2 sec.
The advance ratio for maneuver was relatively low, μ=0.093
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 20
Disk Loading in the LRL Roll Reversal Maneuver
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 21
LRL Roll Reversal Maneuver
The high level BVISPL concentrated in the forward area at beginning of the right roll (t =7.24 s)
The very large BVISPL levels ahead of the rotor at t = 8.25 s and t = 8.65 s are primarily caused by BVI loading during Revs 36 and 37
As helicopter returns to level flight, both advancing and retreating side BVI are present (t = 10.66 s)
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 22
Summary for Roll Reversal Maneuver
In these maneuvers, BVI noise dominates
BVI noise during a transient maneuver is different than in steady flight
Vortex bundling Dynamic state of vortex system (not steady after start of
maneuver)
The formation of the vortex bundle and its subsequent interaction with the rotor blades was strongly influenced by the pilot overshoots in the turn-entry maneuver
Due to the short duration of maneuver duration, the helicopter is constantly in the transient maneuver state and the noise generated in this condition can be considered as transient maneuver noise
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 23
Accomplishments
2004 Accomplishments Limited noise prediction system validation against wind
tunnel measurement for both thickness and loading noise Systematically unraveling the source of maneuver noise
Transient maneuver noise for climb, acceleration maneuver flights.
Compute maneuver noise with BVI using UMD maneuver wake
Rotor wake interaction analyzed for elemental maneuvers Roll maneuver, quick stop, roll reversal maneuvers
2005 Planned Accomplishments Investigate issues of signal processing for aperiodic
conditions RCAS maneuver model with free vortex-wake model
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 24
Milestones 2001 2002 2004 2005CODE DEVELOPMENT:•Initial aircraft motions and complete rotor motions •Validate with WOPWOP•Self-scheduling parallel implementation• Coordinate transformation enhancements•Acoustic analysis of non-periodic time history data•“Flight-test” modeling (GENHEL coupling)•Efficiency enhancements (real-time?)
ANALYSIS•Determine spatial regions where noise depends strongly on wake.•Simple maneuvers analysis •Simple flight path and attitude determination•Validation (with data – flight or wind tunnel)•Advanced wake modeling (RCAS or UMD maneuver wake)
2003
Schedule and Milestones
CompleteIn Progress / Near TermLong TermMoved from last year’s schedule
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 25
Technology Transfer Activities
Papers: AHS Specialists’ Meeting, San Francisco, Jan 2004 AIAA Aerospace Science Meeting and Exhibit, Jan 2004 AIAA/CEAS Aeroacoustics Conference, May 2005 AHS Annual Forum, Grapevine, TX, June 2005
Other Interactions: Collaboration with Gordon Leishman, University of
Maryland Work with Professor Horn: GENHEL coupling and work
toward acoustic prediction capability in new flight simulator
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 26
Recommendations at the last review (2004)
It is recommended to pick concrete physical problems and a firm plan is needed to solve physics or physical mechanisms, such as effects of roll or Lock number on noise. And also validation of analysis is needed for steady flight first, before deeply involved with maneuvering flight conditions.
Actions Taken (2004) Some validation for steady flight
performed Focus on physical mechanisms of
associated with aircraft roll, including BVI noise in maneuver
Gaining understanding of role of BVI and nonimpulsive noise in maneuver
Leveraging or Attracting Other Resources or ProgramsDURIP equipment funding for RCOE
124 processor RCOE parallel clusterRotorcraft flight simulator with acoustic simulation capability
NASA LaRC contract for high-speed maneuver noise prediction modifications to PSU-WOPWOP (Burley/Boyd)Teamed with Georgia Tech for DARPA “Helicopter Quieting” ProjectPhase I SBIR with Continuum Dynamics for real-time rotor noise prediction (NASA LaRC)
Other Impact
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 27
Any Questions … ?
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 28
Auxiliary Presentation Material
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Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 29
Validation of GENHEL/PSU-WOPWOP: Comparison with Wind Tunnel Data
Normalized TimeA
cou
stic
Pre
ssu
re(P
a)
0 0.25 0.5 0.75 1-40
-20
0
20
Microphone 1, MAT=0.796
Normalized Time
Aco
ust
icP
ress
ure
(Pa
)
0 0.25 0.5 0.75 1-40
-20
0
20
Microphone 7, MAT=0.796
Normalized Time
Aco
ust
icP
ress
ure
(Pa
)
0 0.25 0.5 0.75 1-20
-10
0
10
20
Microphone 1, MAT=0.690
Normalized Time
Aco
ust
icP
ress
ure
(Pa
)
0 0.25 0.5 0.75 1-20
-10
0
10
20
Microphone 7, MAT=0.690
Side View
Microphone 7
30 Deg.
1. 5 D
Microphone 1
Top View
1.5 D
1.5 D
In-plane Microphones
measured (Visintainer et al., 1993)
Predicted (GENHEL/PSU-WOPWOP)
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 30
80-Second Maneuver Flight Simulation
Helicopter gross weight: 74800N 4-bladed articulated main rotor and tail
rotor Main rotor radius: 8.18 m
Maneuver Start Time End Time
Level t = 0 sec t = 1 sec
Climb t = 1 sec t = 14 sec
Acceleration t = 1 sec t = 18 sec
Level t = 14 sec t = 22 sec
Coordinated Turn t = 22 sec t = 56 sec
Level t = 56 sec t = 80 sec
La
tera
lCyc
lic(%
)
20
55
90
Lo
ng
.Cyc
lic(%
)
30
45
60
Pitc
hA
ng
le(d
eg
)
-15
-5
5
Ro
llA
ng
le(d
eg
)
-5
15
35
Ya
wA
ng
le(d
eg
)
-10
100
210
Co
llect
ive
(%)
30
50
70
Time (sec)
Ad
v.R
atio
0 20 40 60 800
0.1
0.2
0.3
Time (sec)
Pe
da
l(%
)
0 20 40 60 8040
55
70
Pilot controlsAircraft response
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 31
Arrested Descent Wake (From UMD, Ananthan & Leishman)
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 32
WOPWOP - Thickness
time (s)
Aco
ust
icp
ress
ure
(Pa
)
0.0255 0.026 0.0265 0.027-140
-120
-100
-80
-60
-40
-20
0
20
40PSU-WOPWOP - Isom thickness
PSU-WOPWOP - Thickness
PSU-WOPWOP ValidationComparison with WOPWOP
Thickness and loading noise predictions validated
Operating conditions:• UH-1H model scale untwisted rotor• MH=0.88
• Observer at 3.09 R in plane• Rotation only (hover)
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 33
Main rotor blade description
Lower surface
Upper surface
Tip
Permeable surface formulation Coupling with CFD
for high-speed-impulsive noise
Object oriented approach Modularity and
flexibility for complex rotor configuration
PSU-WOPWOP Features
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 34
Arrested Descent Maneuver
Starts from 6º flight path angle and μ=0.186.
A half-doublet collective pitch input applied between t = 5 and t = 6 s.
At the end of the maneuver, the helicopter is pitched up by over 20º.
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 35
Acoustic Pressure Prediction
Free Vortex-Wake Model
– ● – Pitt-Peters Inflow ModelObserver location Ψ=135º, 22º below the helicopter and 7R away.
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 36
Summary For Arrested Descent
This arrested descent maneuver is a simple maneuver by applying collective pitch input.
In the steady descent condition, BVI is not dominant source of noise due to steep flight path angle.
In this maneuver, the primary effect of the maneuver is that the rotor wake goes through the rotor disk resulting in several BVIs in the rear of the disk that are nearly parallel to the rotor blade during the interactions.
Less BVIs were observed after the maneuver due to helicopter attitude.
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 37
X (m)
Z(m
)
De
cele
ratio
n(m
/s2)
0 20 40 60 80-3
-2.5
-2
-1.5
-1
-0.5
0
-4
-2
0
2
4
6
8heightdeceleration
time (s)
colle
ctiv
ep
itch
(de
g)
0 0.5 1 1.5 2-2
0
2
4
6
8
Arrested Descent
• Case Description– Initial condition: 3 degree steady
descent– Total time: 2 sec – Flight speed: 40 m/s
0 100 200 300-2
0
2
4
6
8
10RollPitchYaw
AircraftAttitude,
deg
X, ftDescent arrested by collective pulse
PENNSTATE1 8 5 5
Kenneth S. Brentner, Dept. of Aerospace Engineering RCOE Review, May 3, 2005 38
time (s)
Aco
ust
icp
ress
ure
(Pa
)
0 0.5 1 1.5 2
-2
0
2
4
6
Sound Pressure Level Computation
Discrete Fourier Transform
Compute sound pressure level
Move slice of
data
• Frequency analysis issues– Non-periodic signal– Noise widely fluctuating in amplitude and frequency
Extract slice of data
Apply Hanning Window