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Mesh Generation

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Alexandros Avdis edited this page Jun 19, 2014 · 12 revisions

Introduction

Fluidity has very limited mesh generation capabilities, and in this context mesh-generation should not be confused with mesh adaptivity. However, mesh generation is an integral part of fluid-flow simulations. The AMCG packages (if you installed with a package manager) include Gmsh, a free mesh generator. Here we go through mesh conventions, formats and list software you can use to generate unstructured meshes

Mesh File Formats

  • Gmsh's msh format, both binary and ASCII (limitations?)
  • Triangle's file format

All surfaces on which boundary conditions are applied should have appropriate boundary IDs, and if multiple regions are used then mesh regions should be assigned appropriate region IDs. See respective mesh generator pages for instructions on how to do this.

Meshes can be generated using any program that outputs triangle meshes, or outputs mesh formats that can be converted to triangle. In particular, there are conversion programs for:

  • Gmsh to triangle : Use gmsh2triangle in tools. If you are generating a 2 dimensional mesh, the default behaviour is to still output 3 dimensional positions. If you require 2d positions in this case (most people will) then you need to supply the --2d option to gmsh2triangle.
  • GiD - gid2triangle, part of fltools
  • GEM - gem2triangle, part of fltools in the legacy branch

Meshes for geophysical simulations

  • Only surface mesh is required
  • Describe how vertical extrusion is done

Mesh Generation Software

  • Gmsh : A versatile 1-, 2- and 3- dimensional mesh generator which may be used to generate meshes for use with fluidity. Gmsh is particularly suitable for setting up idealised test cases and industrial type problems in which the domain is composed of flat surfaces and simple curves. Gmsh is open source. It is included in the AMCG packages, otherwise it is easy to install via: ''' wajig install gmsh '''
  • Cubit : Brief description
  • Qgis meshing plugins : brief description

Mesh Decomposition

If you want to run a simulation in parallel you must partition your mesh. Running Fluidity in parallel includes instructions on how to do this.

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