If more cells are required on a boundary, they can be added using boundary adaption, which allows you to mark or refine cells in the proximity of the selected boundary zones. The ability to refine the grid near one or more boundary zones is provided because important fluid interactions often occur in these regions. Example, development of strong velocity gradients in the boundary layer near a wall.
An example of a grid that can be improved with boundary adaption is shown in Figure 26.3.1. This mesh has only two cells on the vertical face of a step. Boundary adaption on the zone corresponding to the face of the step can be used to increase the number of cells, as shown in Figure 26.3.2. This procedure cannot increase the resolution of a curved surface. Therefore, if more cells are required on a curved surface where the shape of the surface is important, create the mesh with sufficient surface nodes before reading it into the solver.