system level cooling, fatigue, and durability analysis … · system level cooling, fatigue, and...

System Level Cooling, Fatigue, and Durability

Analysis via MultiphysicsAnalysis via MultiphysicsCo-SimulationStuart A. Walker, Ph.D.

[email protected]

Outline

• Motivation• Presentation of process• Presentation of tools• Presentation of the results• Presentation of the results

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Importance of External Automotive Aerodynamics via CFD

Cooling• Engine• Transmission• Brakes

Comfort• Ventilation• Heating• Air conditioning• Wind noise

Stability• Directional• Cross wind sensitivity

Visibility• Dirt (soiling)• Splash/spray• Wiper lift off

Performance

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• Brakes• Condenser

Performance• Fuel economy• Emission• Max. speed• Acceleration

downforce

dragforce

Spoiler oscillation, FSI

Aero acoustics (CAA)

Importance of System Level Modeling• Many important component level

responses – Temperature– Stress– Displacement

• Component responses are coupled via external aerodynamics,

Rotor/Brake Pad Friction

(hot side boundary conditions)

Rotor/Brake Pad Friction


External Aerodynamics

(cold side boundary conditions)

External Aerodynamics


via external aerodynamics, structural physics, and control systems

– Rotor example

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AcuSolve Coupled Model

Heat Transfer Simulation to calculate rotor temperaturesHeat Transfer Simulation to calculate rotor temperatures

Thermo-structural Model

(durability and fatigue)



Outline


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Engine Block Cooling Example• Desired result:

– Temperature in engine block– Stress in engine block– Displacement in engine block

• Important CFD physics– Underhood flow for HTC on engine block– Water jacket flow for engine block cooling

• Modeling approach– Compute HTC from external aero calc– Compute temperature in solid from internal water jacket model– Compute stress/displacement in solid

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General Approach

Subcase 1:

• Bolt Pretension in Head Bolts

Subcase 1:



Combustion Simulation


Combustion Simulation


Heat Transfer Simulation to calculate Heat Transfer Simulation to calculate

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Subcase 2:

• Lock Pre-tension Displacements• Apply Temperature Loading

Subcase 2:


Subcase 3:

• Lock Pre-tension Displacements• Continue Temperature Loading• Apply Combustion Pressure Loading

Subcase 3:


Heat Transfer Simulation to calculate Engine Temperature loading

Heat Transfer Simulation to calculate Engine Temperature loading

External Aerodynamic Simulation


External Aerodynamic Simulation


External Aero Modeling• External aerodynamics drive component level cooling

– Engine block cooled by underhood flow– Radiator cooled by underhood flow– Brake rotors cooled by flow through the wheel well

• Underbody Thermal Management– Fluid flow– Energy Transport– Energy Transport– Porous media

• Analysis– Fluid and solid – Velocity and pressure– Temperature– Drag/lift

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Component Level ModelingComponent designs

– Exhaust systems– Radiator– Blower/Fans– Water jacket HX

Detailed analysis– Fluid and solid– Fluid and solid– Velocity and Pressure– Temperature

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System Level Modeling• Thermal management

– External aerodynamics– Component level modeling

• Coupling for stress analysis– AcuSolve– Radioss

Friction / Motor Dissipation / Combustion


Friction / Motor Dissipation / Combustion


External Aero/HX Simulation


External Aero/HX Simulation


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Heat Transfer Simulation to calculate Engine Loading

Heat Transfer Simulation to calculate Engine Loading





Thermo-Structural Model

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Outline


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Modeling and Visualization Tools

• “One team – One solution”• Altair Engineering, Inc.

– HyperWorks Suite provides an integrated environment for pre/solve/post for system environment for pre/solve/post for system level vehicle coupling of FEA, CFD, MBD, and NVH physics

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Pre-Processing• AcuConsole

– Dedicated pre-processor for AcuSolve– Fast and robust CFD meshing (e.g. 90Mio tetras external automotive

80min)

• HyperMesh– Solver neutral CFD grid generator

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– Solver neutral CFD grid generator– Powerful geometry cleanup/generation tools– One pre-processor for structural and CFD analysis

HyperMesh AcuConsole

Solver• Radioss CFD/FSI

– Explicit multi-physics solver– Coupled solver (structure + fluid)– Suited for compressible flow

• AcuSolve– Implicit multi-purpose CFD solver– Implicit multi-purpose CFD solver– Finite element based– Strong FSI capabilities (P-FSI, DC-FSI)

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Courtesy of HTTAcuSolve Radioss

AcuSolve• General

– General purpose, 3-dimensional, unstructured CFD solver

– Based on Finite Element method (Galerkin Least Square, GLS)

• Originated at Stanford University by Prof. T.J.R. Hughes et. al. and further improved for industrial applications

– Incompressible, weakly compressible Navier Stokes solver

• Numerics

– 2nd order accuracy (space and time) for all flow variables

– Scalable (e.g. customer runs on 1024 CPUs, 350Mio cells)

– Various turbulence models available (RANS, LES, DES)

– Transient / steady state

– Solving the fully coupled system

– Sliding mesh (rotating machinery)

– Moving/deforming mesh, ALE (Fluid-Structure)

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Post-processing• AcuFieldView

– Dedicated CFD post-processor (OEM version of FieldView, Intelligent Light)– Supports only AcuSolve results– Client-server architecture, 8 way parallel

• HyperView– Solver neutral CFD post-processor– Showing structural and CFD results – Showing structural and CFD results

in one framework

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HyperView

eigenmodes

pressure Top. Optim. streamlines

AcuFieldView

CFD Optimization with HyperWorksInitial design Morphing Optimization Optimized design

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Cw = 0.04Cw = 1

UI = 0.83 UI = 0.94

Component Level OptimizationSuccess Story (CFD optimization)

Case: Exhaust system, catalytic converterObjective: uniform flow, min. pressure dropResult: uniformity +12%, pressure drop -16%

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Case: Engine compressor, impeller bladeObjective: maximize pressure ratioResult: pressure ratio +5.6%,

Case: Evaporator, HVAC systemObjective: uniform flow, min. pressure dropResult: uniformity +5.6%, pressure drop -7%

Outline


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External Aero Solution• Closed shell mesh generated in HyperMesh

– Shell mesh boolean– CFD wrapping

• Starting point for “The Virtual Wind Tunnel”– Ease of use– AcuSolve behind the scenes

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External Aero Solution

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External Aero Results

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Engine Block Loading

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Static FEA Analysis in OptiStruct

Subcase 1:


Subcase 1:



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Subcase 2:


Subcase 2:


Subcase 3:


Subcase 3:


Temperature Results

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Cylinder Head

Displacement Results

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Stress Results

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Contact Pressure and Bore Deformation

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Conclusion• Altair HyperWorks Suite provides a

complete vehicle simulation package– Pre-processing

• HyperMesh/AcuConsole• Virtual Wind Tunnel

– Solver• AcuSolve – CFD• OptiStruct/Radioss – FEA• OptiStruct/Radioss – FEA

– Post-Processing• HyperView/AcuFieldView

– CFD/FEA Optimization• HyperMorph/HyperStudy

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Stuart Walker, Ph.D. | CFD Specialist [email protected] | altair.com

Altair | Innovation Intelligence®

system level cooling, fatigue, and durability analysis … · system level cooling, fatigue, and...

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