Dealing with Non-Flat Faces in OpenFOAM

Dealing with Non-Flat Faces in OpenFOAM

Non-flatness in mesh faces can cause issues in OpenFOAM simulations, particularly with finite volume discretization. Here are several approaches to handle non-flat faces:

Prevention During Meshing

1. Use quality meshing tools:

   • snappyHexMesh: Set proper feature capturing and mesh quality controls
   • cfMesh: Has good handling of complex geometries
   • ANSA, HyperMesh, or other CAD-based meshers with OpenFOAM export

2. Mesh quality parameters:

   // In snappyHexMeshDict or other mesher dictionaries
   maxNonOrtho 65;  // Maximum non-orthogonality
   maxConcave 80;   // Maximum concavity
   minFlatness 0.5; // Minimum face flatness (0-1)
   

Post-Meshing Solutions

1. Check mesh quality:

   checkMesh -allGeometry -allTopology
   

   Pay attention to “Face flatness” and “Face concavity” warnings.

2. Face splitting:

   • Use splitMesh or splitMeshRegions to divide problematic faces
   • Or implement face splitting in your meshing process

3. Mesh smoothing:

   foamyHexMesh -parallel
   # or
   surfaceRefineRedGreen
   

4. Manual correction:

   • Use autoPatch to identify problematic faces
   • Edit the mesh with topoSet and refineMesh

Simulation-Time Solutions

1. Numerical schemes:

   // In system/fvSchemes
   divSchemes
   {
       default         Gauss linear;
       // More robust schemes for bad meshes
       div(phi,U)      Gauss limitedLinear 1;
   }
   

2. Relaxation factors:

   // In system/fvSolution
   relaxationFactors
   {
       fields
       {
           p           0.3;
       }
       equations
       {
           U           0.7;
       }
   }
   

3. Non-orthogonal correctors:

   // In system/fvSolution
   PIMPLE
   {
       nNonOrthogonalCorrectors 2;
   }
   

Advanced Techniques

1. Polyhedral meshing:

   • Polyhedral cells can better handle non-flat faces
   • Use polyDualMesh to convert to polyhedral mesh

2. MPPIC or Lagrangian methods:

   • For multiphase flows, these may be more robust

3. Custom boundary conditions:

   • Implement special BCs that account for face non-flatness

Remember that prevention through quality meshing is always better than fixing issues later. Always check your mesh quality before proceeding with simulations.

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资料

OpenFOAM源码位置

src/mesh/snappyHexMesh/refinement*
src/meshCheck/*