For simulations using turbulence models, you can describe the wall surface as being smooth or rough. For rough walls, the equivalent sand-grain roughness is required as input parameter. An additional modeling option, High Roughness (Icing), is available when using the SST turbulence model. The details of the rough wall treatment for turbulence models based on the and – equation can be found in Treatment of Rough Walls in the CFX-Solver Theory Guide.

This option is not available for the Free Slip wall boundary condition, or when a turbulence model is not used (that is, Laminar).