Development and Application of Partioned Methods for … 445.6 Wing Flutter Analysis • Flow...
Transcript of Development and Application of Partioned Methods for … 445.6 Wing Flutter Analysis • Flow...
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EXCELLENCE IN SIMULATION TECHNOLOGIES
Development and Application of Partioned Methods for Large Scale FSI Problems
Philippe GeuzaineCFD-MP Group, Cenaero
Email: [email protected]
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Sample Targeted Applications
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Unsteady Aeroelastic Response
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Four-field Formulation
Heat Transfer Fluid (ALE)
Structure Fluid Mesh
Temperature(Displacements) Force Mesh Motion
TemperatureHeat flux
DisplacementsVelocities
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Aero- & Elasto-Dynamic Data Exchange
• Interpolation across non matching interfaces (accuracy and conservation)
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Exchange With Non-Matching Interfaces
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Example of Displacement Exchange
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Data Exchange & Code Coupling
• Dynamic data communication between CSD and CFD modules
• Available tools (integration platforms) for interpolation and/or data communication– MpCCI (Fraunhofer Institute SCAI)– MDICE (CFD RC)– SimServer (EADS)– PALM (CERFACS)– CALCIUM (EDF)– SALOME (EDF/CEA)– ...
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Fluid Mesh Motion
• Spring-type analogy• No node collapse• No face penetration• Mesh recovery
(after one oscillation cycle)• Mesh shearing?
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CFD on Moving Grids
• Navier-Stokes equations on fixed grids
• Arbitrary Lagrangian Eulerian (ALE) formulation on moving grids
• The discrete geometric conservation law (DGCL) can guide the selection among the multiple accuracy preserving ALE extensions
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Additional Issues for Nonlinear FSI
• Non specific issues (CAD to mesh generation, turbulence modeling, nonlinear structural effects modeling, ...)
• Modularity & compatibility with existing tools (plug-and-play/off-the-shelf approach)
• Speed & turnaround time– Second-order accurate & robust coupled time-
integration for large time-steps– Parallel computing
• Verification & validation
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Monolithic Schemes for Coupled Systems
• Single time-integrator (system of first-order semi-discrete equations)
• Solution at the nonlinear level (single set of equations for fluid, fluid mesh and structure)– Newton type method
• Solution at the linear level (very large system)– Single approach (direct, iterative)– Partioned or staggered approach (block Jacobi, block
Gauss-Seidel)
• Appealing for accuracy and stability, but issues for software modularity
• Demonstrated usually for academic problems
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Partioned Schemes for Coupled Systems
• Collocated staggered approach
• Loosely-coupled scheme (maximize efficiency)• Strongly-coupled scheme (similar monolithic)
CSD
CFD
CFD Mesh
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Individual Time-integrator Selection
• Second-order accurate time-integrators (necessary condition to achieve second-order time-accuracy for the coupled system)
• Newmark scheme (with the equilibrium written at time level tn+1) for the CSD solver (no mass or stiffness matrices exported from the CSD solver)
• ALE version of the three-point backward difference scheme for the CFD solver (not trivially second-order time-accurate on moving meshes)
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Sample Predictors and Correctors
• Structural displacement predictor
• Aerodynamic force corrector
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Control Parameters Design
• Control parameters– Structural displacement predictor– Mesh integrator– Aerodynamic force corrector
• Preserve second-order time-accuracy of individual time-integrators (three-point backward difference and Newmark schemes)
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AGARD 445.6 Wing Configuration
• Nonlinear flow model (inviscid Argo model)• Linear structural model (SAMCEF Mecano model)• Steady & unsteady aeroelastic analyses• Flutter analysis
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CFD Meshes
22,014 points
178,938 points
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Steady Simulation
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Unsteady Simulations
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Time-Accuracy Analysis
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Unsteady Simulations with P/C
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Unsteady Simulations with Large Δt
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AGARD 445.6 Wing Flutter Analysis
• Flow conditions: 0.5 < M < 1.141 (zero incidence)• Density taken from Yates’ experiment• Pressure adjusted to produce flutter• Coupling time-step Δt = 1 ms• Flutter index definition
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Response at Mach = 0.957
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Flutter Frequency
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Flutter Index
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CAD-based Wing MDO
CAD : CATIAV5
AutomaticMesh Generation
Parallel Aeroelastic Computation
Argo + Samcef
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Optimization Workflow with Minamo
UserUserSpecifications
Approximate ModelANN, RBF, Kriging, …
OptimizationOptimizationEA, gradient-based, …
Performance Check
DATABASEDATABASE
Accurate Model Accurate Model CFD / Structure / Exp. / ...
END
ONLINE modeling
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Simulation Workflow with Argo/Samcef
Design Variables
Inviscid Aeroelastic Computation
CFD CSD
Wing Deformed Shape
Viscous Computation
CFD
Lift & dragStress, buckling,tip displacement
CAD generation& meshing
Meshing with Boundary Layers
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Wing Parameterization
Tip chord
Root chord
Span
Sweep angle
twist
Angle ofattack
3 spars
10 ribs
Stringers 1 Stringer
s 2 Stringers 3 Stringer
s 4 Stringers 5
Panels 1 Panels
2Panels
3
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Optimized Stringers and Planform
• Objective: wing mass reduction• Constraints: L/D, stress, buckling
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Future Work on Supersonic Transport
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Aerothermoelasticity Challenge at Mach 5