Response of Channel Flow to Roughness Heterogeneity

Abstract

The hydrodynamic response of turbulent flow in an open channel to the bed and bank roughness heterogeneity was demonstrated. Roughness‐induced secondary currents were numerically simulated in the presence of the vortex induced by the free surface, and the two vortices induced by the channel corner. The relative importance of these sources for lateral motion was examined. Turbulence was modeled by the energy dissipation model, combined with the algebraic stress model suggested by Naot and Rodi (1982). The three‐dimensional flow was solved using the parabolic pressure correction algorithm of Patankar and Spalding (1972). The examples suggest that the dominant presence of the strong vortex, which is induced by the free surface, restricts the effects of the roughness heterogeneity to the lower part of the channel. Still, major differences in the structure of turbulence near the channel bed are shown.