Dataset for DNS-based characterization of pseudo-random roughness in minimal channels

In addition to the global flow properties, the distribution of time-averaged surface force exerted by the roughness onto the fluid is calculated and compared for different cases. It is shown that patterns of surface force distribution over irregular rough surfaces can be well captured when the sheltering effect is taken into account. This is made possible applying the sheltering model proposed by Yang et al. to each specific roughness topography.

Furthermore, an analysis of the coherence function between roughness height and surface force distributions reveals that the coherence drops at larger streamwise wavelengths, which can be an indication that very large horizontal scales are less dominant in contributing to the skin friction drag. Finally, some existing roughness correlations are assessed using the present roughness dataset, and it is shown that the correlation predictions for the values of equivalent sand-grain roughness mainly lie within $\pm30\%$ error in comparison to the DNS results.