![Configuring dynamicTopoFvMesh
//- Options for dynamicTopoFvMesh
dynamicTopoFvMesh
{
//- Should all options be made mandatory?
//- Useful for first-time use.
allOptionsMandatory no;
//- Set run-time debug level [0-5]
// debug 0;
//- Specify the number of threads
threads 1;
//- Specify re-meshing interval
//- Negative value implies no re-meshing
interval 1;
//- Specify whether the length-scale field
//- should be dumped to disk
dumpLengthScale false;
Slide: 22/31](https://image.slidesharecdn.com/mooneyslides-250505140951-14eb6bb5/85/mooney-slides-for-dynamic-topoFvMesh-in-open-foam-for-mesh-motion-31-320.jpg)
![Governing Equations
Newtonian Stress Tensor:
σ = −pI + τ
τ = µ[∇v + (∇v)T
]
Incompressible Navier Stokes Equations:
Z
S
n · v dS = 0
d
dt
Z
V
ρv dV +
Z
S
n · ρ(v − vs)v dS =
Z
V
ρg dV −
Z
V
∇p dV +
Z
S
n · (µ∇v) dS](https://image.slidesharecdn.com/mooneyslides-250505140951-14eb6bb5/85/mooney-slides-for-dynamic-topoFvMesh-in-open-foam-for-mesh-motion-48-320.jpg)
![Conditions at a Fluid Interface
Dynamic Condition:
Z
S
n · σ2 dS −
Z
S
n · σ1 dS +
Z
∂S
mσ dL = 0
Differential Form:
(p2 − p1)n − n · (τ2 − τ1) = ∇sσ + κσn
Normal Stress Balance:
(p2 − p1) − nn: (τ2 − τ1) = κσ
Tangential Stress Balance:
n · (τ2 − τ1) − n[nn: (τ2 − τ1)] = −∇sσ](https://image.slidesharecdn.com/mooneyslides-250505140951-14eb6bb5/85/mooney-slides-for-dynamic-topoFvMesh-in-open-foam-for-mesh-motion-50-320.jpg)
mooney slides for dynamic topoFvMesh in open foam for mesh motion
- 1. Using the dynamicTopoFvMesh class in OpenFOAM Sandeep Menon Kyle Mooney Multi-phase Flow Simulation Laboratory University of Massachusetts Amherst June 13 2011
- 2. Introduction Examples I Leaky Faucet (free surface flow) I Micron Scale Droplet Collision (free surface flow) I Translating Circle (2D parallel remeshing) I Cylinder Intake Stroke (internal flow) I Store Separation (external flow & six-DOF) Adaptive reconnection methods I Mesh quality optimization I Length scale resolution Solution remapping Parallel mesh reconnection Setting Up A Case I Configuring dynamicMeshDict I Running A Simulation Slide: 2/31
- 3. Droplet formation under gravity Slide: 3/31
- 4. Droplet formation under gravity Slide: 4/31
- 5. Micron Scale Droplet Collision Slide: 5/31
- 6. Translating Circle in Domain No Redistribution Redistribution every 100 time steps Slide: 6/31
- 10. Governing Equations Integral Conservation Law for Moving / Deforming Control Volumes: d dt Z V ρφ dV + Z S n · ρ(v − vs)φ dS = − Z S n · qφ dS + Z V sφ dV Conservation of Mass: d dt Z V ρ dV + Z S n · ρ(v − vs) dS = 0 Conservation of Linear Momentum: d dt Z V ρv dV + Z S n · ρ(v − vs)v dS = Z V ρg dV + Z S n · σ dS Space Conservation Law: d dt Z V dV − Z S n · vs dS = 0 Slide: 10/31
- 11. Mesh Smoothing Objectives: Continuously maintain mesh quality No changes to mesh connectivity Delay local re-meshing requirements Easily incorporated into conservation laws Slide: 11/31
- 12. Mesh Smoothing Objectives: Continuously maintain mesh quality No changes to mesh connectivity Delay local re-meshing requirements Easily incorporated into conservation laws Spring Analogy Laplacian: X j kij(xij − xi) = 0 Laplacian Smoothing on Surfaces: (I − nnT ) X j kij(xij − xi) = 0 Slide: 11/31
- 13. Adaptive Mesh Reconnection Reconnection for Improved Mesh Quality Handle excessive distortion Used when mesh-motion algorithms are insufficient Localized nature to avoid interpolation errors Only simplical 2D and 3D meshes considered Reconnection for Length-Scale Resolution Accurately capture physical phenomena Achieve trade-off for computational cost vs. solution accuracy Slide: 12/31
- 14. Adaptive Mesh Reconnection Edge Swapping Edge Bisection and Collapse Slide: 12/31
- 15. Adaptive Mesh Reconnection Slide: 12/31
- 16. Adaptive Mesh Reconnection Slide: 12/31
- 18. Solution Remapping Supermesh Steps Compute intersections Compute and limit gradients on source mesh Volume and distance weighted Taylor series interpolate to supermesh Agglomeration on target mesh Slide: 13/31
- 19. Solution Remapping Steps Compute intersections Compute and limit gradients on source mesh Volume and distance weighted Taylor series interpolate to supermesh Agglomeration on target mesh φ(xKb ) = 1 VKb " n X i=1 {φKa + (xi Kc − xKa ) · (∇φ)Ka }V i Kc # Slide: 13/31
- 21. Parallel Mesh Reconnection Shared memory parallelism Entire memory is accessible to all compute nodes Thread-safety is always a concern Using the pthreads library for thread handling Limited by memory bandwidth / capacity Distributed memory parallelism Each compute node sees only its share of memory Inter-processor communication using MPI Theoretically infinite memory capacity Slide: 14/31
- 22. Parallel Mesh Reconnection Halo meshes Slide: 14/31
- 23. Parallel Mesh Reconnection Halo meshes Slide: 14/31
- 24. Configuring dynamicMeshDict Dictionary Organization: Smoothing and dynamicMesh Library Selection Smoother Options Define Explicit Patch Motion General dynamicTopoFvMesh Options I Refinement Options Parallel Redistribution Options Slide: 15/31
- 26. Configuring dynamicMeshDict //- Select the type of dynamicFvMesh dynamicFvMesh dynamicTopoFvMesh; //- Select the type of motionSolver solver mesquiteMotionSolver; Slide: 17/31
- 27. Configuring mesquiteOptions Subdict. mesquiteOptions { //- Specify interval for surface smoothing surfInterval 1; //- Optimization metric optMetric AspectRatioGamma; //- Objective function objFunction LPtoP; //- Optimization algorithm optAlgorithm FeasibleNewton; //- Termination criteria sub-dictionaries //- (takes default values if not specified) //- Specifying an empty sub-dictionary //- terminates with available options tcInner { absGradL2 1e-4; cpuTime 0.5; } Slide: 18/31
- 28. Configuring mesquiteOptions Subdict. cont. //- Power value for the LPtoP objective function pValue 2; power 2; //- Specify a tolerance for the surface-smoothing CG solver tolerance 1e-2; //- Specify number of CG sweeps for surface-smoothing nSweeps 2; //- Specify slip patches for the motionSolver slipPatches { sideWall; topWall; } Slide: 19/31
- 29. Configuring mesquiteOptions Subdict. cont. //- Constrain surface mesh-motion on a specified cylinder cylindricalConstraints { //- Specify options per slip patch sideWall { axisPoint (0.0 0.0 0.0); axisVector (0.0 0.0 1.0); radius 1.0; } } Slide: 20/31
- 30. Configuring mesquiteOptions Subdict cont. //- Specify fixedValue patches for the motionSolver fixedValuePatches { topWall { type angularOscillatingDisplacement; amplitude -0.0125; //type oscillatingDisplacement; //amplitude (0 0 -0.01); axis (1 0 0); origin (0 0 3); angle0 0.0; omega 0.15; value uniform (0 0 0); } } Other fixedValuePatch types can be found here: /src/dynamicMesh/meshMotion/fvMotionSolver/pointPatchFields/derived //-End of Mesquite options Slide: 21/31
- 31. Configuring dynamicTopoFvMesh //- Options for dynamicTopoFvMesh dynamicTopoFvMesh { //- Should all options be made mandatory? //- Useful for first-time use. allOptionsMandatory no; //- Set run-time debug level [0-5] // debug 0; //- Specify the number of threads threads 1; //- Specify re-meshing interval //- Negative value implies no re-meshing interval 1; //- Specify whether the length-scale field //- should be dumped to disk dumpLengthScale false; Slide: 22/31
- 32. Configuring dynamicTopoFvMesh //- sliverThreshold specifies the //- quality criteria for sliver removal. sliverThreshold 0.35; //- Should the tool attempt to remove slivers //- that fall below the sliverThreshold value? removeSlivers false; //- Skip mapping step. Useful while using //- this tool as a pre-processor // skipMapping true; // Toggle edgeRefinement on/off edgeRefinement yes; //- If the number of modifications are to be limited, set this option // maxModifications 1000; //- Load custom libraries for metrics // tetMetricLibs ("libtetMetrics.so"); //- Tetrahedral mesh quality metric tetMetric Knupp; Slide: 23/31
- 33. Configuring dynamicTopoFvMesh::refinementOptions //- Options for edge-bisection/collapse. //- The edgeRefinement flag must be set for //- the following options to have effect refinementOptions { collapseRatio 0.5; bisectionRatio 1.5; growthFactor 1.03; //- By default, existing boundary edge-lengths //- are used for length-scales. //- Length-scale can be fixed for certain patches. fixedLengthScalePatches { topWall 0.2; bottomWall 0.2; sideWall 0.2; outlet 0.2; } Slide: 24/31
- 34. Configuring dynamicTopoFvMesh::refinementOptions //- Avoid refinement on certain patches, if necessary noModificationPatches {} //- Set floating length-scale values on certain patches freeLengthScalePatches {} //- Limit lengthScales to specified values, if necessary // minLengthScale 0.1; // maxLengthScale 0.3; //- Field-based refinement options // fieldRefinement gamma; // fieldLengthScale 0.005; // lowerRefineLevel 0.001; // upperRefineLevel 0.999; // maxRefineLevel 4; // meanScale 0.015; Slide: 25/31
- 35. Droplet Formation: Setup Slide: 26/31
- 36. Droplet Formation: growthFactor Slide: 27/31
- 37. Store Separation: Setup Slide: 28/31
- 38. Fixed Displacement: Setup Patch motion can be explicity perscribed in the motionSolver subdictionary Slide: 29/31
- 39. Limitations Topology changes on simplicial elements only (Tri & Tet) I Some success in mixed element meshes by tagging zones for topo changes Crushing Cells I Currently does not support cell “crushing” I Example: complete valve closure for cylinder simulations I Potentially performed via coupling with a GGI patch Serial version available in 1.6-ext release. Parallel redistribution still a little buggy. (Consider it Beta) Slide: 30/31
- 40. Discussion and Future Work Slide: 31/31
- 41. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Slide: 31/31
- 42. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Highly versatile application range Slide: 31/31
- 43. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Highly versatile application range Conservative solution transfer Slide: 31/31
- 44. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Highly versatile application range Conservative solution transfer Efficient due to shared / distributed memory parallelization Slide: 31/31
- 45. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Highly versatile application range Conservative solution transfer Efficient due to shared / distributed memory parallelization Future focus: I Constrained, cost-effective remapping for divergence-free fluxes I Testing / validation of two-phase flows I Handling of coalescence and separation regimes Slide: 31/31
- 46. Discussion and Future Work Successful implementation of mesh-topology modification algorithms Highly versatile application range Conservative solution transfer Efficient due to shared / distributed memory parallelization Future focus: I Constrained, cost-effective remapping for divergence-free fluxes I Testing / validation of two-phase flows I Handling of coalescence and separation regimes Thank You Slide: 31/31
- 47. Extra slides
- 48. Governing Equations Newtonian Stress Tensor: σ = −pI + τ τ = µ[∇v + (∇v)T ] Incompressible Navier Stokes Equations: Z S n · v dS = 0 d dt Z V ρv dV + Z S n · ρ(v − vs)v dS = Z V ρg dV − Z V ∇p dV + Z S n · (µ∇v) dS
- 49. Conditions at a Fluid Interface Dynamic Condition: Z S n · σ2 dS − Z S n · σ1 dS + Z ∂S mσ dL = 0
- 50. Conditions at a Fluid Interface Dynamic Condition: Z S n · σ2 dS − Z S n · σ1 dS + Z ∂S mσ dL = 0 Differential Form: (p2 − p1)n − n · (τ2 − τ1) = ∇sσ + κσn Normal Stress Balance: (p2 − p1) − nn: (τ2 − τ1) = κσ Tangential Stress Balance: n · (τ2 − τ1) − n[nn: (τ2 − τ1)] = −∇sσ
- 51. Conditions at a Fluid Interface Dynamic Condition: Z S n · σ2 dS − Z S n · σ1 dS + Z ∂S mσ dL = 0 Kinematic Condition: n · v2 − n · v1 = 0 Momentum transfer: (I − nn) · v2 − (I − nn) · v1 = 0 Continuity of Velocity: v2 = v1
- 52. Mesh Smoothing Local Optimization: Gauss-Seidel iteration over vertices Maximize quality of local cell-group Global convergence is unclear
- 53. Mesh Smoothing Local Optimization: Gauss-Seidel iteration over vertices Maximize quality of local cell-group Global convergence is unclear Global Optimization: Maximize quality of all elements simultaneously Typically involves large, sparse-matrices Attempts to find a global optimum May not adequately penalize worst quality cells
- 54. Mesh Smoothing Algebraic Mesh Quality Metric Mean Ratio = 12(3V 2 )1/3 P6 i L2 e
- 55. Solution Remapping Repeated remapping tests Source field Inverse distance weighting First order conservative Second order conservative