Ansys Meshing – Mesh Types (Hexa, Prism, Polyhedral)

The cell shape you choose changes how many cells you need, how well they align with the flow, and how fast each iteration runs.

Hexahedra are the most efficient when the geometry allows them: fewer cells for the same resolution, and faces that can be aligned with the flow direction, which cuts numerical diffusion. Tetrahedra fill any geometry automatically, at the cost of more cells and worse alignment. Prisms sit in between and are what inflation layers are made of, since they stack cleanly along a wall. Polyhedral cells have many neighbours each, which helps the gradients converge and usually reduces the cell count compared with a tetrahedral mesh of the same fineness.

In practice most CFD meshes are mixed: hexahedra or polyhedra in the bulk, prisms along the walls, tetrahedra wherever the geometry is too awkward for anything else.