This tab is available when the Consider surface roughness option is selected on the "Main" tab.
Surface Roughness Properties
If the texture of the model surfaces has a major effect on the results, you can define the parameters in this area. They will be applied to every surface of the model during the calculation.
For the program to determine the turbulent viscosity near the surfaces, the "Height of sand-grain roughness" Ks needs to be specified. You can define the size of the sand grains in the text box or table column for each material.
The "Roughness constant" Cs controls the shape and spacing of the sand grains. This parameter is set as 0.5 by default, assuming a homogeneous distribution. If there is non-uniform roughness, Cs can be increased up to 1.0.