Table of Contents


snappyHexMesh is a fully parallel, split hex, mesh generator that guarantees a minimum mesh quality. Controlled using OpenFOAM dictionaries, it is particularly well suited to batch driven operation.

Key features:

  • starts from any pure hex mesh (structured or unstructured)
  • reads geometry in triangulated formats, e.g. in stl, obj, vtk
  • no limit on the number of input surfaces
  • can use simple analytically-defined geometry, e.g. box, sphere, cone
  • generates prismatic layers
  • scales well when meshing in parallel
  • can work with dirty surfaces, i.e. non-watertight surfaces


The overall meshing process is summarised by the figure below:

snappyHexMesh overview

This includes:

  • creation of the background mesh using the blockMesh utility (or any other hexahedral mesh generator)
  • extraction of features on the surfaces with surfaceFeatureExtract utility
  • setting up the snappyHexMeshDict input dictionary
  • running snappyHexMesh in serial or parallel

Evolution of the snappy mesh for the iglooWithFridges tutorial is shown below:


Meshing controls are set in the snappyHexMeshDict located in the case system directory. This has five main sections, described in the following sections:

  • geometry: specification of the input surfaces
  • castellatedMeshControls: starting from any pure hex mesh, refine and optionally load balance when running in parallel. The refinement is specified both according to surfaces, volumes and gaps
  • snapControls: guaranteed mesh quality whilst morphing to geometric surfaces and features
  • addLayersControls: prismatic layers are inserted by shrinking an existing mesh and creating an infill, subject to the same mesh quality constraints
  • meshQualityControls: mesh quality settings enforced during the snapping and layer addition phases

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