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In this presentation an aerodynamics computational analysis for a partially-dressed, cavity-closed nose landing gear configuration is discussed. The primary objectives of this study are to obtain a full representation of the flow, to compare the computational results against experimental data, to validate the solution and present the capabilities of the software used. For preparing and performing this external aerodynamic analyses, commercial software tools HyperMesh and AcuSolve were utilized, which enable the geometry manipulation, mesh generation and problem solution. AcuSolve is a general purpose CFD solver, applying the Galerking/Least-Square (GLS) finite element methodology to solve the Navier-Stokes equations on an unstructured mesh topology (Hughes et al. 1989, Shakib et al. 1991). In the presented vertical solution, steady state and transient CFD simulations including Spalart-Allmaras and Detached-Eddy Simulation (DES) for turbulence modeling are performed. For this study a 1/4 scale model of a Gulfstream G550 aircraft nose landing gear is investigated, which was already tested in NASA Langley Research Center in Basic Aerodynamic Research Tunnel (BART). All simulations performed yielding very good results, with overall good agreement with the existing experimental data from NASA. In general, key strong characteristics of HyperMesh and AcuSolve, accuracy, efficiency and robustness were presented.
Citation preview
Innovation Intelligence®
7th European ATC
CFD analysis on Gulfstream G550 nose
landing gear
Dr. Konias A. Fotis
June 24-26, 2014 | Munich, Germany
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Overview
• Introduction
• Problem description
• Geometry preparation
• Meshing
• Results – Validation
• Conclusions
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Introduction
• Aerodynamics computational analysis for Gulfstream 550 nose landing gear
model with
partially-dressed, cavity-closed
Galerkin/Least-Square (GLS) finite element methodology
Objectives
Full representation of the flow
Results comparison against
experimental for validation
Software capabilities
presentation
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Problem description
• 1/4-scale high-fidelity replica of a Gulfstream G550 nose landing gear
Model height = 449mm
Wheels diameter = 137mm
• Experimental data from closed-wall Basic Aerodynamic Research Tunnel (BART)
at NASA Langley Research Center (LaRC)
Test area dimensions:
H 700mm x W 1000mm x L 3000mm
700m
m
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Flow conditions
• Incompressible air flow
Mach = 0.166 => Uinlet = 56.6 m/sec
Reynolds = 73,000 (based on the diameter of the shock strut l = 0.01905m)
Total Pressure inlet = 101,464 N/m2 Dynamic viscosity= 1.85313e-5 kg/m·s
Temperature = 23.28 oC Density of air = 1.25 kg/m3
Static Pressure outlet = 99,241 N/m2
Turbulence viscosity ratio = 1.0 => Eddy viscosity inlet = 1.482504e-005 m2/sec
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Software used
v12 for geometry clean-up and meshing
v12 for pre-processing
v12 for processing
v12 for post-processing
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Geometry clean-up
• IGS file geometry import
• Surfaces organized in different components
Surfaces grouping according to deferent parts
• Removal of redundant surfaces and geometries
Only external shell surfaces are needed
• Detect and repair of free edges
Formation of watertight model
• Repair of distorted geometries
• Minor geometry alterations
1st Option: Addition of missing joint connections
2nd Option: Closure of small gaps and proximities
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Surface organize and removal
redundant
surfaces
Surfaces
grouped by
part
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Repair of free edges and formation of watertight model
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Repair of distorted geometries
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Minor geometry alterations
• 1st Option : Addition of missing joint connections
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Minor geometry alterations
• 2nd Option : Closure of small gaps and proximities
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Meshing configuration
• 2D triangular surface mesh
2 cases, 1 for each geometry option
The same base configurations for all cases
2D automesh / surface deviation (before scale)
Refinement at closed volume proximities, narrow passages and corners
Coarser mesh for wind tunnel’s walls
Approximately 990,000 surface elements
• 3D tetrahedral mesh
3 cases of different first element height
Estimated Y+ <1 Approximately 78 million elements in total
>> Y+ <5 >> 60 million >>
>> Y+ <100 >> 40 million >>
Multiple groups of Boundary Layers for every case
3 Refinement boxes for core elements
upstream, around and downstream of geometry
Same core mesh configurations for all cases
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
2D Surface mesh details
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Proximity and narrow openings refinement
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2D Meshing in small gaps
1st Geometry option 2nd Geometry option
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3D Tetrahedral mesh overview
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Boundary Layers – Estimated Y+ at same spot
Y+ < 100
First height = 0.25mm
Growth rate = 1.2
No of layers = 6
Y+ < 5
First height = 0.01mm
Growth rate = 1.2 / 1.4 / 1.5
No of layers = 6 / 5 / 5
Y+ < 1
First height = 0.002mm
Growth rate = 1.2 / 1.3 / 1.4 / 1.5
No of layers = 6 / 6 / 5 / 5
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Boundary layer details
Dynamic BL reduction
Y+ < 100
Y+ < 100
Y+ < 5
Y+ < 5
Dynamic BL reduction
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Summary of mesh models
• 4 different case were studied in total
1) Estimated
2nd geometry option with closed small gaps and proximities
3 groups of Boundary layers in total, across whole model
2) Estimated
1st geometry option with no geometry alterations
4 groups of Boundary layers in total, across whole model
3) Estimated
2nd geometry option with closed small gaps and proximities
4 groups of Boundary layers in total, across whole model
4) Estimated
2nd geometry option with closed small gaps and proximities
5 groups of Boundary layers in total, across whole model
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
AcuConsole pre-processing setup
• Preliminary 1st stage transient simulation, to wash out initial solutions
Problem Description
Analysis type: Transient
Turbulence equation: Spalart Allmaras
Auto Solution Strategy
Max time steps: 600
Initial time increment: 0.0001 sec
Nodal Output
Solution projected as Nodal Initial Condition for 2nd stage
• Main 2nd stage transient simulation, for final results
Problem Description
Analysis type: Transient
Turbulence equation: Detached Eddy Simulation
Auto Solution Strategy
Max time steps: 20,000
Initial time increment: 5e-006 sec
Nodal and Running Average Output
Nodal Initial Condition from 1st stage
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AcuConsole boundary conditions setup
• Problem description
Analysis type : Transient
Flow equations : Navier Stokes
Abs. Pressure Offset = 0 Pa
Surface name BC Conditions
Inlet
Type: Inflow
X velocity = 56.6 m/sec
Eddy visc. = 1.482504e-5 m2/s
Outlet Type: Outflow
Pressure: 0.0 N/m2
Wind Tunnel Slip walls
All surfaces Non-slip walls
Inlet Non-slip
Floor
Outlet
Model surfaces
Wind Tunnel
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Surfaces Y+ results
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Average Velocity magnitude at center line plane
(Y=0m)
Y+ < 5 No gaps closed
Y+ < 100
Y+ < 5
Y+ < 1
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Average Velocity magnitude at wheel axis plane
(Z=0.381m)
Y+ < 100 Y+ < 1
Y+ < 5 Y+ < 5 No gaps closed
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Ave Velocity vectors at wheel axis plane (Z=0.381m)
Y+ < 100 Y+ < 1
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Comparison with experiment: avg z-vorticity at wheel
axis (Z=0.381m)
Y+ < 100
Y+ < 1
Y+ < 5
Y+ < 5 No gaps closed
Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.
Comparison with experiment: avg X velocity at wheel
axis (Z=0.381m)
Y+ < 1
Y+ < 5
Y+ < 5 No gaps closed
Y+ < 100
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Comparison with experiment: Cp around wheel
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Conclusions and references
• Conclusions
• Strong available tools for a very good representation of the flow
• Overall good agreement with experimental results
• Good mesh sensitivity analysis
• References
1. Hughes T., Franca L., Hulbert G., A new finite element formulation for computational fluid dynamics. VIII. The
Galerkin/Least-Square method for advective-diffusive equations. Computer Methods in Applied Mechanics
Engineering, 73, 1989, pp 173-189.
2. Shakib F., Hughes T., Johan Z., A new finite elements formulation for computational fluid dynamics.X. The
compressible Euler and Navier-Stokes equations. Computer Methods in Applied Mechanics Engineering, 89,
1991, pp 141-219.
3. Neuhart, D.H., Khorrami, M.R., Choudhari, M.M., Aerodynamics of a Gulfstream G550 Nose Landing Gear
Model, AIAA Paper 2009-3152, 2009.
4. Zawodny, N.S., Liu, F., Yardibi, T., Cattafeta, L.N., Khorrami, M.R., Neuhart, D., Van de Ven, T., “A
Comparative Aeroacoustic Study of a ¼-Scale Gulfstream G550 Aircraft Nose Landing Gear Model,” AIAA
Paper 2009-3153, 2009.
5. Veer N. Vatsa, David P. Lockard, Mehdi R. Khorrami, Jan-Renee Carlson, Aeroacoustic Simulation of a Nose
Landing Gear in an Open Jet Facility using FUN3D, AIAA Paper 2010-4001, 2010.