dlr results of the sixth aiaa computational fluid dynamics drag
TRANSCRIPT
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DLR Results of the Sixth AIAA Computational Fluid Dynamics Drag Prediction Workshop
Stefan Keye, Vamshi Togiti, Olaf Brodersen
Institute for Aerodynamics and Flow Technology
German Aerospace Center (DLR) Braunschweig, Germany
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Contents
• Introduction
• Case 2 - CRM Nacelle-Pylon Drag Increment
• Case 3 - CRM WB Static Aero-Elastic Effect
• Side-of-Body Flow Separation
• Case 5 - CRM WB Coupled Aero-Structural Simulation
• Conclusions
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Introduction - Computational Grids -
• Started Grid Generation from Fine (F) Level.
• Derived coarser Grids through scaling of Sources, Factor 1/1.51/3 = 0.873…
• Generated Meshes compliant to Gridding Guidelines, two Exceptions: • Wing & Nacelle TE Base >> 8 Cells reduced (2 Cells inboard, 7 Cells outboard). • Wing spanwise Spacing increased from < 0.1%×Semi-Span at Root/Engine to ~0.34%.
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
Name WB WBNP
∆y1 / [in] GG SOLAR GG SOLAR
Tiny (T) ~20 7.15 25-30 11.8 0.001478 Coarse (C) ~30 14.1 40-45 23.2 0.001285 Medium (M) ~45 26.8 60-70 44.9 0.001118 Fine (F) ~70 39.7 85-100 81.1 0.000972 Extra Fine (X) ~100 × 130-150 × 0.000845 Ultra Fine (U) ~150 × 190-225 × 0.000735
Grid Size Factor: ~1.9×
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Introduction - Test Cases, Grids & Turbulence Models -
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
Config. Grid Case 2 Case 3 Case 5
WB
T SA-neg, RSM-ω -- -- C SA-neg, RSM-ω -- -- M SA-neg, RSM-ω SA-neg, RSM-ω SA-neg F SA-neg, RSM-ω -- --
WBNP
T SA-neg, RSM-ω -- -- C SA-neg, RSM-ω -- -- M SA-neg, RSM-ω -- -- F SA-neg, RSM-ω -- --
• Slow Convergence with RSM-ω on fine Grids, not finished yet.
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Introduction - Flow Solver TAU -
• Finite-Volume
• Node-centered
• LU-SGS Time Integration
• 4w Multigrid Cycle
• Steady RANS
• Central spatial Discretization Scheme
• TAU Release 2015.2.0 with new Matrix Dissipation Formulation
• Turbulence Models: • Negative Spalart-Allmaras One-Equation Model (SA-neg), 2012 • SSG/LRR-omega Full Reynolds Stress Model (RSM-ω), 2012
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Case 2 - CRM Nacelle-Pylon Drag Increment
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
CFD Computations on all Grids fall within the specified Accuracy of CL = 0.5+/-0.0001.
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Case 2 - CRM Nacelle-Pylon Drag Increment
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Case 2 - CRM Nacelle-Pylon Drag Increment
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Case 3 - CRM WB Static Aero-Elastic Effect
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Case 3 - CRM WB Static Aero-Elastic Effect
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Side-of-Body Flow Separation - Overview -
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
• Predicted by linear Eddy Viscosity Models.
• Size reduced when taking into Account non-isotropic turbulent normal Stresses.
• Not found with k-ω or RSM Models.
• Size depends on: • numerical Dissipation, • Angle of Attack, • Grid Density, • …
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Side-of-Body Flow Separation - Variation with Grid Size …
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
Separation Size increases for finer Meshes.
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Side-of-Body Flow Separation - Variation with Grid Size and Angle of Attack -
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
Separation Size increases for finer Meshes.
Separation Size increases with Angle of Attack.
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Case 5 - CRM WB Coupled Aero-Structural Simulation
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
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Case 5 - CRM WB Coupled Aero-Structural Simulation
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.
α / [deg] CL CD CD,p CD,f CMy Case 2 2.3753 0.50003 0.02570 0.01420 0.01150 -0.1008 FSI 2.4034 0.50001 0.02604 0.01457 0.01148 -0.1019
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Conclusions
• Family of four SOLAR Grids generated on WB and WBNP Configurations (Tiny to Fine).
• Grid Sizes smaller than required by Gridding Guidelines, Size Factor larger.
• CFD Data for two Turbulence Models (SA-neg, RSM-ω) available.
• Differences between Grid Sizes and Turbulence Models very small.
• Deviations in Drag Increment between CFD and NTF Test Data below 2 drag counts.
• Deviations in Shock Location between SA-neg and RSM-ω increase with Angle of Attack.
• SoB Separation Size increases with both Grid Size and Angle of Attack.
• Good Agreement between coupled Simulation and CFD on pre-deformed Geometry.
6th AIAA CFD Drag Prediction Workshop, 16 -17 June 2016, Washington, D.C.