When you are modeling turbulent flows in
FLUENT using the Spalart-Allmaras
model, you must provide the boundary conditions for
in addition to
other mean solution variables. The boundary conditions for
walls are internally taken care of by
FLUENT, which obviates the need for
your inputs. The boundary condition input for
you must supply to
FLUENT is the one at inlet boundaries (velocity inlet, pressure inlet,
etc.). In many situations, it is important to specify correct or realistic
boundary conditions at the inlets, because the inlet turbulence can
significantly affect the downstream flow.
See Section 7.2.2 for details about specifying the boundary condition for at the inlets.
You may want to include the effects of the wall roughness on selected wall boundaries. In such cases, you can specify the roughness parameters (roughness height and roughness constant) in the panels for the corresponding wall boundaries (see Section 7.13.1).