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Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
Aerodynamic Simulations with AcuSolve
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Aerodynamic Simulations with AcuSolve

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  • 1. Innovation Intelligence®Aerodynamic Simulations with AcuSolveDr. Marc RatzelApril 2013
  • 2. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Agenda1. Motivation• Applications of aerodynamics2. AcuSolve for external aerodynamics• Quick overview of AcuSolve3. Aerodynamic examples• Automotive aerodynamics• Fluid-Structure-Interaction for a 100m wind turbine4. Summary
  • 3. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.1. Motivation• Aerospace• No ground effects• A380  900 km/h (Mach 0.75)• Interest: lift/drag ratio, stall point, capacity,…• Automotive• Proximity to the ground• My car  150 km/h (Mach 0.13)• Interest: drag, lift, noise,…• Buildings• Several objects in close proximity• Avg. wind speed  20 km/h (Mach 0.02)• Interest: pressure loads, max. speed,…
  • 4. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Characteristics of external flows• Numerical model• Large models (+50Mio volume elements)• Complex geometry (e.g. engine, underbody)• Very fine mesh near walls (Boundary layer, BL)• Physics• Different scales time/length scales(e.g. sounds travels much faster than airflow,high/low frequency, small/large eddies)• Turbulence• Transient phenomena (e.g. airborne noise CAA, wake)• Fluid-Structure-Interaction(e.g. structural vibration of hood  noise, eigenmodes)• Discontinuities (e.g. shock wave aerospace)• Moving boundaries (e.g. train, wheels of a car)Boundary layer meshTurbulent wake, wind turbineShock wave
  • 5. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.2. AcuSolve (CFD solver)• General• General purpose, 3-dimensional, unstructured solver• Based on Finite Element method (GLS)• Originated at Stanford University (T. Hughes et al.)• Integration with other HyperWorks tools (HyperMesh, HyperView, RADIOSS,..)• Numerics• 2nd order accuracy in time and space for all flow variables• Designed from day one for large scale problems• Advanced turbulence models (SST, k-w, SA, DES, DDES, …)• Comprehensive physics (fan/radiator component, sliding mesh, radiation,…)• Robust fast volume mesher included (e.g. 90Mio car, engine, underbody, 80min)• Very low requirement for element quality (e.g. tetras in boundary layer, skew>0.999)Excellent fit for external aerodynamics
  • 6. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.AcuSolve (Fluid-Structure-Interaction, FSI)• Rigid body dynamics• 6 DOF rigid body solver• No structural displacement• Practical FSI (P-FSI)• No run-time coupling• Structural displacement computed in AcuSolve based on eigenmodes• Limited to linear structural displacement• Directly coupled FSI (DC-FSI)• Codes communicate during run-time• Loads/displacement exchange• Non-linear structural behaviour• Supported for RADIOSS, Abaqus, MD-Nastran
  • 7. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.3.1 Automotive aerodynamics• Drag force• Accounts for 75% of the car’s resistance (100km/h)• Computation:• Drag reduction by minimizing CD  shape optimization• Drag coefficients CDdrag sideliftCar shape Frontal areaModern car: ~ 0.29 Eiffel Tower: 1.8 – 2.0 Man (upright): 1.0 – 1.3
  • 8. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Asmo model (Daimler & Volvo)Amed body (S.R. Ahmed)C_p, underbody C_p, rear C_p, roofDrag coeff.: 0.162 (exp) / 0.164 (AcuSolve)Drag coeff.: 0.23 (exp) / 0.23 (AcuSolve)Classical external aero benchmarksAcuSolveExp. (Volvo, Daimler)
  • 9. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Fluid-Structure-interaction for rear wing• P-FSI analysis• Generic model of an automotive rear wing• Soft plastic material, thickness of 2mm• 20 & 100 eigenmodes computed with OptiStructfixedmonitor pointDisplacement of monitor point(20 & 100 eigenmodes)Down force for rigid and elastic4%
  • 10. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Fluid-Structure-interaction for rear wing• P-FSI analysis• Generic model of an automotive rear wing• Soft plastic material, thickness of 2mm• 20 & 100 eigenmodes computed with OptiStructfixedmonitor pointStructural deformation (vel. contour) Structural deformation (vel. contour)
  • 11. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Altair’s Virtual Wind Tunnel (VWT)• External automotive CFD analysis• Advanced physics (rot. wheels, radiator, FSI,…)• Efficient case setup
  • 12. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Altair’s Virtual Wind Tunnel (VWT)• External automotive CFD analysis• Advanced physics (rot. wheels, radiator, FSI,…)• Efficient case setup• AcuSolve as CFD solver• Automatic post-processing
  • 13. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.3.2 Wind turbine (Fluid-Structure-Interaction analysis)• Facts• Cooperation with Sandia National Laboratories, CA, USABlade length 100mWeight 1.1tMax. chord 7.6mMaterial Fiberglass, Resin, Foam,…Max. operation speed 7.44 RPM (tip speed 80m/s)Power output ~ 13MWhuman scale 1.8m
  • 14. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Numerical models• Structural model• OptiStruct used as solver (eigenmode analysis)• Composite model• 100 eigenmodels• CFD model• Steady state, Multiple-Reference-Frame (MRF)• Spalart-Allmaras RANS turbulence model• ~ 50Mio elementsinflow periodicoutflowfarfieldbladeNot true to scaleEigenmodeCFD mesh
  • 15. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.Results (varying inflow speed & rotor RPM)• Surface streamlines• Power / Thrust4.0 m/s Wind Speed 17.0 m/s Wind SpeedLarger separation bubbleDiscrepancy with FAST resultsSome discrepancy(due to separation bubble)Remark: FAST and WT_Perf are commonly used tools in the wind turbine domain, containing simplifications for the CFD part
  • 16. Copyright © 2012 Altair Engineering, Inc. Proprietary and Confidential. All rights reserved.4. Summary• Challenges for external aero• Large complex models (+50Mio cells)• Advanced physics (e.g. diff. scales, turbulence)• Transient (e.g. FSI, noise)• AcuSolve• Accurate, scalable, robust CFD solver• Fluid-Structure-Interaction (FSI) capabilities• Altair’s Virtual Wind Tunnel for external automotive aero• Aerodynamic examples• Automotive: Classical benchmarks (ASMO, Ahmed)& FSI rear wing• Wind turbine: FSI of turbine blade• Both cases  very good match with exp. dataParking turbine bladeVirtual Wind Tunnel

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