Boundary layer flows are performed in a fashion similar to external flows with one important exception. Since the pressure field is generally uniform throughout the domain in these types of flows, the nodal pressures must be initialized to the same value (usually zero) and not updated during the calculation. The solution relaxation for pressure must be set to zero to maintain the initial pressure field.
Note that there will be finite 
terms in the governing flow equations since “intermediate” pressures are used in their computation. “Intermediate” refers to a point in the middle of a sequential solver iteration when pressure gradients are established to conserve mass. At the end of each sequential solver iteration, these pressure gradients will not be present since pressure relaxation is set to zero.