Toward modeling of turbulent flow over surfaces of arbitrary roughness

The problem of Reynolds-averaged modeling turbulent boundary-layer flow over surfaces arbitrary roughness is studied using the results direct numerical simulations many different rough surfaces. complexity in sublayer such that most effective general strategy appears to be model it as a prescribed velocity profile, either at coarse level conventional roughness-specific log-linear wall function, or fine modeled profile across sublayer, together with standard closure outer flow. Calculations made sandgrain functions and velocity-profile models were excellent agreement channel-flow simulation data and, after correction for effects Reynolds number height, good friction coefficients wide range reference pipe-flow data. Equally predictions flows wavy walls, walls spaced arrays semi-ellipsoids, elements random size orientation, when profiles corresponding roughnesses used. This approach possible by availability relevant from library roughness-sublayer kinds