2020/06/29 by Gaute Linga, Luiza Angheluta, Linga, Gaute +3
Engineering · Environmental Science · #76-10 #Computational Physics (physics.comp-ph) #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Hydrology and Sediment Transport Processes #Particle Dynamics in Fluid Flows
paper · pdf · doi:10.48550/arxiv.2006.16169
openalex publication_date 2020/06/29 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Using 3D direct numerical simulations of the Navier--Stokes equations, we study the effect of wall roughness on the onset of turbulence in channel flow. The dependence of the friction factor on the Reynolds number, Re, is found to follow a generalized Forchheimer law, which interpolates between the laminar and inertial asymptotes. The transition between these two asymptotes occurs at a first critical Re, Rec, that depends nontrivially on the roughness amplitude. We identify the transition from subcritical to supercritical onset by looking at the dependence of the velocity fluctuations on Re for different roughness amplitudes. We find that this second critical Re is comparable in magnitude to Rec, implying that transitional flow is an integral part of flow in open fractures when Re and the roughness amplitude are sufficiently high.