Adaptive Tetrahedral Remeshing for Multiphase Flow Simulations in OpenFOAM Sandeep Menon and David P. Schmidt Multiphase Flow Simulation Laboratory University of Massachusetts Amherst June 3, 2009
Jul 27, 2015
Adaptive Tetrahedral Remeshingfor Multiphase Flow Simulations in
OpenFOAM
Sandeep Menon and David P. Schmidt
Multiphase Flow Simulation LaboratoryUniversity of Massachusetts Amherst
June 3, 2009
Off-center Droplet Collision
M. Dai and D. P. Schmidt,
“Numerical Simulation of Head-On Droplet Collision: Effect of Viscosity on Maximum Deformation”,
Phys. Fluids, 17(4), 2005.
Motivation
Pros and Cons:Accurate interface representation.Direct application of interface boundaryconditions.Conserves mass very well.Complicated mesh manipulation withlocalized remeshing and interpolation.
Lagrangian interface tracking:Interface points move with the interfacenormal velocityThe interior mesh automatically adjusts tomaintain mesh qualityWe only use simplical meshes
Prior Work
Since last year:Two-dimensional version in OF completedDemonstrated for ink jetsPublished in ILASS 2008, ICLASS 2009
Interface tracking capabilities in OpenFOAM:interTrackFoam - Prior work on interfacetracking by Zeljko Tukovic and Hrvoje Jasak.Uses the freeSurface library, also developedby Tukovic and Jasak.Used mesh-motion only - limited deformationcapability.tetDecomposition mesh motion solver.
Three Major Code Components
Incompressible PISO solverMesh motionMesh reconnections
Tetrahedral Mesh Motion
Current state of techniques:Laplacian smoothing - fast,simple, but createsdegenerate cells.Need to associate meshmotion with mesh quality.Alternative:optimization-basedsmoothing.Optimize algebraic meshquality metrics.More expensive thanLaplacian smoothing, butvery effective.
Tetrahedral Mesh Motion
Mesquite Optimization Library:Developed by Sandia NationalLabs.OpenFOAM wrapper class -mesquiteSmoother.Run-time selection of:É Optimization algorithms: CG,
Steepest Descent, FeasibleNewton, Quasi Newton, etc.
É Quality metrics: ConditionNumber, Inverse Mean Ratio,Aspect Ratio, etc.
É Termination Criteria: RelativeQuality Improvement, L2 norm,iterations, CPU Time, etc
Mean Ratio =12(3V2)1/3∑6
iL2e
Atomic Topology Operations
Arbitrary number of tetrahedra sharing an edge.Dynamic Programming algorithm to define swap configuration.
3D Edge Flip2D Edge Flip
Combination of Swap Operations
3-2 swapEquitorial Polygon2-3 swap4 cells sharing an edge
Possible Configurations
7 sides, 42 ways
6 sides, 14 ways5 sides, 5 ways
Tetrahedral Bisection and Collapse
Test Case: Rotating & Translating Sphere
Test Case: Rotating & Translating Sphere
Test Case: Rotating & Translating Sphere
Ink Jet Simulation
Conclusion
Future work...Automated interface topology modifications for dropletbreak-up and coalesence.Effective divergence-free local interpolation.Hybrid parallelization efforts: MPI and pthreads.
Work In Progress...Non-Newtonian effects.Temperature-dependent viscosity and surface-tension effects.