Tdyn reference manual
In many real applications, there is a frequent difficulty in defining some of the boundary conditions at the inlet and outlet of a calculation domain in the detail that is needed for an accurate simulation. A typical example is the specification of turbulence properties (turbulence intensity and length scale) at the inlet flow boundary, as these are rarely available for a new design configuration. Other examples are the specification of the boundary layer velocity profile on the walls at an inlet, or the precise distribution of a species concentration at an inlet boundary.
Next a brief list of recommendations about boundary conditions prescription is given.