Tetrahedra mesher
In this section we are going to give elements about the tetrahedra mesher we have chosen to use here for meshing our different geometries. We are going to work with the case of the semicylinder.

ICEM Tetra automatically fills an arbitrary space and voids enclosed by an assembly of CAD patches with tetrahedron elements. There are several options for improving and modifying tetrahedral meshes. We are going to explain here the two options : the Smoother and the Coarsener.

No Smoother, No coarsener

We have explained how to mesh the geometry in the "Creating a semicylinder" part. But like this, the mesh is not optimised because it doesn't use tools of optimisation as the Smoother and the Coarsener.

So without Smoother and without Coarsener, the mesh is like above (following different views) :

Mesh without Smoother and without Coarsener (green: wall - blue: symetry - yellow: outlet and inlet)

We can notice that the mesh is formed by a structured assembly (in hexadral) of tetrahedron elements. It is not a optimal mesh which should be formed by more unstructured assembly of elements.

The Smoother

The tetrahedral smoother first calculates the relative aspect ratio (obtained by calculating the ratio between the volume of the element and that of the largest tetrahedron that could fit inside the sphere that circumscribes the actual one) of each cell. The user specifies the quality limit and number of iterations (Aspect Ratio and Iterations).
The smoother then modifies elements below the quality criteria. Nodes are moved and merged, edges are swapped, and in some cases elements are deleted. The operation is automatically repeated on the improved grid, up to the specified number of iterations.

Mesh with the Smoother and without Coarsener

The Coarsener

The coarsener reduces the number of triangles in a mesh by merging multiple triangles into one.
There is one parameter to regle for the Coarsener: Aspect Ratio to increase more or less the propriety of the Coarsener.

Mesh with the Smoother and the Coarsener

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