Abstract
The DANS/DEM (Double Averaged Navier Stokes / Discrete Element Method) model, dedicated to the prediction of roughness effects [Chedevergne20,Chedevergne21,Chedevergne23], is tested against a DNS database [Yang22] of channel flows with rough walls that notably emphasizes the influence of the Skewness of the roughness elevation map. An in-depth analysis of the DNS database proved that the separation zones occurring in the vicinity of the wall play a non-negligible role as the Skewness becomes negative. To try to account for the influence of these zones, the pressure gradient imposed in the simulated channel is made variable with the wall distance in the roughness sublayer. However, for roughness distribution with negative Skewness, an increase of the turbulent mixing is also observed in the DNS, that may be accounted for in the DANS/DEM model by modifying the source term involved in the transport equations of the turbulent scalars.