Numerical Simulation for Blood Flow - Microsurgery: Advances, Simulations, and Applications - page 192

If the solution method can be applied on an unstructured grid
with cells of varying topology, the grid generation program is subject
to few constraints. For example, local grid reinement by subdivision
of cells into smaller ones is possible. A non-reined neighbor cell,
although it retains its original shape (e.g., hexahedron), becomes
a logical polyhedral since a face is replaced by a set of sub-faces.
The solution domain can irst be divided into blocks that can be
subdivided into grids with good properties; one has the freedom
to choose the best grid topology (structured H-, O-, or C-grid, or
unstructured tetrahedral or hexahedral grid) for each block. The
cells on the block interfaces then faces of regular shape and have
to be treated as polyhedra. An example of such a grid is shown in
Fig. 5.19. The grid contains a block interface on which the faces are
irregular. The generation of grids with non-matching interfaces
is much simpler than creation of a single-block grid itted to the
whole domain. We again note that the solution method has to allow
treatment of polyhedral CVs with an arbitrary numbers of faces.

Figure 5.19 Polyhedral volume mesh with prism layered mesh.