A fast and direct method for characterizing hydraulic roughness

Abstract

We describe a fast direct numerical simulation (DNS) method that promises to directly characterize the hydraulic resistance of any given rough surface, from the hydrauli-cally smooth to the fully rough regime. The method circumvents the unfavorable computational cost associated with simulating high-Reynolds-number flows by employing minimal-span channels (Jimenez & Moin, 1991). Proof-of-concept simulations, employing the parametric-forcing roughness model (Busse & Sandham, 2012), demonstrate that flows simulated in minimal-span channels are sufficient for capturing the downward velocity shift predicted by flows in full-span channels. Owing to the minimal cost, we are able to conduct parametr..