yes, the drag force report should be in the -ve z direction. Similar to the flow.nMy recommendations, continue running the case for sometime until you get converged residuals ... if you still find unlogic results or the residuals do not converge, run the case in unsteady.nOne question, I know you are comparing with the literature, but was the wheel hanging in the other paper? ... why don't you put it just above the lower wall?n