8.3 The Choice of Velocity Components
223
choose the best grid topology (structured H-, 0-, or C-grid, or unstructured
tetrahedral or hexahedral grid) for each block. The cells on the block interfaces then have faces of irregular shape and have to be treated as polyhedra.
An example is shown in Fig. 8.4; the grid contains a block interface on which
the faces are irregular. Generation of grids with non-matching interfaces is
much simpler than creation of a single-block grid fitted to the whole domain.
We again note that the solution method has to allow treatment of polyhedral
CVs with an arbitrary numbers of faces; how this can be achieved will be
shown below and cell-wise local grid refinement is discussed in Chap. 11.
Fig. 8.4. A grid created by combining two blocks with a non-matching interface
and cell-wise local refinement (courtesy of ICCM Institute of Computational Continuum Mechanics GmbH; grid generated using the Cometpp grid generator); note
the interface with irregular cell faces
If, on the other hand, the solution method requires all CVs to be of a
particular type, generation of grids for complex geometries may be difficult.
It is not unusual for the process of grid generation to take days or even
weeks in some industrial applications of CFD. An efficient grid generator is
an essential part of any CFD package.
8.3 The Choice of Velocity Components
In Chap. 1 we discussed issues associated with the choice of components of
the momentum. AS indicated by Fig. 1.1, only the choice of components in
223
choose the best grid topology (structured H-, 0-, or C-grid, or unstructured
tetrahedral or hexahedral grid) for each block. The cells on the block interfaces then have faces of irregular shape and have to be treated as polyhedra.
An example is shown in Fig. 8.4; the grid contains a block interface on which
the faces are irregular. Generation of grids with non-matching interfaces is
much simpler than creation of a single-block grid fitted to the whole domain.
We again note that the solution method has to allow treatment of polyhedral
CVs with an arbitrary numbers of faces; how this can be achieved will be
shown below and cell-wise local grid refinement is discussed in Chap. 11.
Fig. 8.4. A grid created by combining two blocks with a non-matching interface
and cell-wise local refinement (courtesy of ICCM Institute of Computational Continuum Mechanics GmbH; grid generated using the Cometpp grid generator); note
the interface with irregular cell faces
If, on the other hand, the solution method requires all CVs to be of a
particular type, generation of grids for complex geometries may be difficult.
It is not unusual for the process of grid generation to take days or even
weeks in some industrial applications of CFD. An efficient grid generator is
an essential part of any CFD package.
8.3 The Choice of Velocity Components
In Chap. 1 we discussed issues associated with the choice of components of
the momentum. AS indicated by Fig. 1.1, only the choice of components in