Rough wall boundary conditions
 

Hello,
I'm a basic OpenFOam user. I've been working on a simulation of a water droplet moving on an inclined surface. Up to now, I've been simulating smooth surfaces with different contact angles. I've been using InterFoam, making the assumption of laminar flow and incompressible fluid. I just had to implement the contact angle in the o/alpha1 file. I now need to model a rough surface. I've read that it is possible only in turbulent flow. I was thinking of using a turbulent model and implementing the nutRoughWallFunction in the 0/nut file. DOes this make sense? DO I need to change something else passing from a laminar to a turbulent model in this particular case? And what's the difference between the nut file and the mut one? Because i read that also a mutRoughWallFunction exists. Is it possible?
I've already tried a couple of simulations but i ended up with a fatal error about "Adjustable delta T" and I'm worried it could be linked to an error in the boundary conditions. is it possible?
Thanks a lot for your help.