Meshing of volumes algorithms

Introduction

Flux provides three generators for automatic meshing of volumes: the ASML mesher, the Delaunay mesher, and the MeshGems mesher.

The three meshers are presented in the blocks below.

MeshGems mesher

MeshGems, by its module MG-Tetra it is a generator of tetrahedral mesh of volume from a mesh of surface triangular. It is marketed by Distene http://www.distene.fr/

ASML mesher

The ASML Mesher (Altair Solid Meshing Library) is a volume mesher which is the proprietary of Altair. This is a mesher of volume mesh starting from a surface mesh. Including ASML allows to generate tetrahedral mesh of volume from a mesh of surface triangular like the module MeshGems-Tetra (which is not the proprietary of Altair).

Delaunay mesher

The mesh generation by the Delaunay mesher is carried out in two phases, as presented in the table and figure below.

Note: The Delaunay mesher is not available if the Dynamic memory is activated (Delaunay is available only with User memory).
Stage Description
1 Generation of boundary mesh
2 Insertion of internal nodes into border mesh elements

Comparison

Comparison of Volume mesh generators is presented in the table below
  Delaunay MeshGems / ASML (Altair Solid Mesher Library)
Characteristics
  • This mesher is the historical mesher of Flux
  • Potentially it rebuild the surface mesh to construct a mesh of volume
  • Respects the surface mesh (not node insertion)
  • Robust mesher=> tested by other simulation tools

Advantages /

disadvantages
  • Relaxation may be important =>Less nodes and less mesh elements
  • More time to mesh the device
  • Difficulty with the extrusive mesh
  • Low relaxation => Increase the number of nodes and the number of mesh elements
  • Low time to mesh the device with good quality of the mesh compared to Delaunay
  • Suitable for mixed mesh
Remember: In 3D, in case of a mixed meshing (mapped mesh /automatic mesh) with the Delaunay mesher, certain nodes must be inserted on the faces during the generation of the mesh front. This insertion is forbidden on the mapped faces, which generates the failure of the Delaunay mesher. The MeshGems and ASML meshers are better suited to this problem.
Note: The ASML mesher was integrated with the Flux 2023 release. It is intended to replace the MeshGems mesher in the long term. The MeshGems mesh generator will disappear in a future version. For this Flux 2023 release, the both meshers can be used, the default mesher is always MeshGems.

Configure the mesher

To configure the volume mesher:

  • clic on: Tools > Geometry and Mesh options > Edit
  • clic on tab Mesh
  • choose the mesher

Mesh optimization

Flux equally provides an algorithm for the optimization of the automatic volume meshing with Delaunay or MesGems meshers (The mesh optimisation is not available with ASML for this first version).

The optimization enables:

  • to improve the mesh quality
  • to reduce the number of elements

Optimization of the process

The mesh optimization is an iterative process of partition and/or fusion of the volume elements in function by certain predefined criteria. The global goal is the improvement of the mesh quality and the reduction of the number of elements.

The number of iterations influences over the quality of the result and the process time:

  • Optimization of average quality and rapid: one iteration
  • Optimization of good quality and slow: five iterations

The default number of iterations is set to 3, a value permitting to obtain a good quality/time ratio.