I'm researching about open channel flow, and the roughness is an important role in open channel. But I don't find where can I set the roughness in FLOW-3D. May Someone help me to solve the problem ?

Thanks a lot.

You may use rough(1)=0.001 (roughness in meters) for example in $obs part of the prepin.inp or use Geometry->component->surface properties->surface roughness and remember that roughness in meters (if you use si system of course). FLOW-3D help has full information about this.

Regards, Armen

It is very easy, F3D get these datas where you define a new obstacle with special material properties in geometry menu.

Very grateful everyone. I'll try again, thanks.