[shindiregita]

Hello, is anyone familiar with drag analysis in turbulent flow due to surface roughness using Ansys Fluent? I could really use your help.

I'm analyzing drag on a flat plate with homogeneous surface roughness and inhomogeneous surface roughness. I'm gonna talk about the homogeneous surface roughness first. I use 3 variations of surface roughness that are equivalent to sand grain roughness: P150 (111 microns), P100 (163 microns), and P60 (264 microns). I use tetra mesh, with y+ slightly over 30 to capture the effects of the surface roughness. I use the k-omega SST turbulence model. I've tried analyzing the drag with all three variations of surface roughness, but the differences between the results were not significant. Somehow, the P60 roughness resulted in a slightly smaller drag than P150 roughness. The validation I'm using is a wind tunnel experiment with the same roughness variations. In that simulation, the results between the roughness variations are quite reasonable, with P60 giving the highest drag.

Up to this point, I am so confused about what had gone wrong that I have been oblivious to. It might have something to do with the physical reasons. If anyone can shed a light on this issue then it would be very much appreciated. Thanks!