Hi all: I have stratified (air-water) flow within a pipe , the water flow in the button of pipe and air in the top and I am use the VOF model. I have the roughness value at interface between the phases from experiments and I did not know how to set it? Is there anybody can assist me with it?

Thanks in advance Saleem

in boundary conditins menu, select and set the conditions for the wall for which you want to set the roughness, then select the momentum panel and set the value for the roughness.