CFD Analysis on Gulfstream G550 Nose Landing Gear

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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.

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CFD Analysis on Gulfstream G550 Nose Landing Gear

  1. 1. Innovation Intelligence® 7th European ATC CFD analysis on Gulfstream G550 nose landing gear Dr. Konias A. Fotis June 24-26, 2014 | Munich, Germany
  2. 2. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Overview • Introduction • Problem description • Geometry preparation • Meshing • Results – Validation • Conclusions
  3. 3. 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
  4. 4. 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 700mm
  5. 5. 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
  6. 6. 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
  7. 7. 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
  8. 8. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Surface organize and removal redundant surfaces Surfaces grouped by part
  9. 9. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Repair of free edges and formation of watertight model
  10. 10. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Repair of distorted geometries
  11. 11. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Minor geometry alterations • 1st Option : Addition of missing joint connections
  12. 12. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Minor geometry alterations • 2nd Option : Closure of small gaps and proximities
  13. 13. 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
  14. 14. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 2D Surface mesh details
  15. 15. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Proximity and narrow openings refinement
  16. 16. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 2D Meshing in small gaps 1st Geometry option 2nd Geometry option
  17. 17. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 3D Tetrahedral mesh overview
  18. 18. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 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
  19. 19. 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
  20. 20. 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
  21. 21. 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
  22. 22. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 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
  23. 23. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Surfaces Y+ results
  24. 24. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Average Velocity magnitude at center line plane (Y=0m) Y+ < 5 No gaps closed Y+ < 100 Y+ < 5 Y+ < 1
  25. 25. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Average Velocity magnitude at wheel axis plane (Z=0.381m) Y+ < 100 Y+ < 1 Y+ < 5 Y+ < 5 No gaps closed
  26. 26. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Ave Velocity vectors at wheel axis plane (Z=0.381m) Y+ < 100 Y+ < 1
  27. 27. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Comparison with experiment: avg z-vorticity at wheel axis (Z=0.381m) Y+ < 100 Y+ < 1 Y+ < 5 Y+ < 5 No gaps closed
  28. 28. 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
  29. 29. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. Comparison with experiment: Cp around wheel
  30. 30. Copyright © 2013 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved. 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.

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