can be represented by their values at discrete
points in space (pi, 
i), forming a grid. The derivatives can be represented by FD
approximations involving neighbouring points, for instance How are we going to discretise these equations? One approach is based on the FD methods
suggested in earlier lectures. The variables p, can be represented by their values at discrete
points in space (pi, i), forming a grid. The derivatives can be represented by FD
approximations involving neighbouring points, for instance
 | (I.3) |
The method most commonly used for engineering problems is the Finite Volume (FV)
method. This is used in most commercial codes - Fluent, STAR-CD, CFX etc. In the FV
method, the flow region is entirely divided into small boxes, called cells or control volumes,
forming a mesh. The equations can be reexpressed in terms of flow into and out of each cell
changing the ammount of the quantity 
inside that cell. This is done by integrating the
equations over the volume of each cell. The result is a set of difference equations which can be
solved numerically as before.
The advantage of doing things this way is that the cells can be any shape required - cubes, tetrahedra, distorted cubes, or more complicated structures.