Turbulence in a Gravel-Bed Stream with an Array of Large Gravel Obstacles

Abstract

AbstractThis experimental and analytical study investigates the double-averaged (DA) turbulent flow characteristics within an array of large gravel obstacles found atop a porous gravel bed. Analysis of the experimental data reveals that the DA streamwise velocity preserves the logarithmic law above the form-induced sublayer, while a linear law and a third-degree polynomial function apply within the form-induced and interfacial sublayers, respectively. The form-induced shear stress is 70% of the DA Reynolds shear stress (RSS) occurring at the virtual bed level. The DA turbulent kinetic energy (TKE) components, streamwise and vertical, attain their peak values at the obstacle crest level, while they diminish sharply below the virtual bed level. The fluxes of the TKE streamwise and vertical components, however, change their signs slightly below the crest level, indicating a changeover of the dominance of the bursting events. For the TKE budget, the TKE production, diffusion, and pressure energy diffusion rat...