Polyhedral / hybrid meshes
Automatic grid generators often produce polyhedrahl and hybrid (polyhedra + hexahedra) meshes. To ensure that these meshes perform as fast as hexahedral meshes, it is necessary to apply suitable numerical corrections.
Correct cell sizes in critical parts of the geometry are essential to the quality of a solution. Following images compare the effects of the thickness (y+) of wall adjacent cells on turbulent kinetic energy k. In the left figure the cells adjacent to the wall are too big and k is overpredicted down-stream. In the right figure y+ has been chosen correctly for the underlying turbulence model (k-epsilon) and local velocities.
The higher precision results are achieved without compromise of computation time.
y+ too big