I am about to run an air flow simulation on a large crane boom assembly and am not seeing an option to set the surface roughness of it anywhere apart from the 'wall' options in boundary conditions. Seeing as this is an external analysis, I wasn't sure if 'wall' is actually talking about the crane boom, or something else. I have gone into the wall boundary conditions and there is an option to select 'Real wall' and some surface options there. I tried to drag select my whole model and apply this, but it causes my computer to hang. So my question is, is this how I set the surface roughness of my parts? And if so, how can I set the surface roughness to my model without it crashing?