Numerical Simulation for Blood Flow - Microsurgery: Advances, Simulations, and Applications - page 191

Figure 5.18 Tetrahedral volume mesh with prism layered mesh.
This approach enhances grid quality near the walls and leads to
both more accurate solutions and better convergence of numerical
solution methods; however, it can be only used if the solution
method allows for mixed control volume types. In principle, any type
of method (FD, FV, FE) can be adapted to this kind of grid.
Another approach to automatic grid generation is to cover
the solution domain with a Cartesian grid and adjust the cells cut
by domain boundaries to it the boundary. The problem with this
approach is that the cells near boundary are irregular and may
require special treatment. However, if this is done on a very coarse
level and the grid is then reined several times, the irregularity is
limited to a few locations and will not affect the accuracy much, but
the degree of boundary irregularity is limited.
To move the irregular cells further away from walls, one can irst
create a layer of regular prisms or hexahedra near walls; the outer
regular grid is then cut by the surface of the near-wall cell layer. This
approach allows fast grid generation but requires a solver that can
deal with the polyhedral cells crated by cutting regular cells with
arbitrary surface. Again, all types of methods can be adapted to this
type of grid.