The Hydrodynamic Response of the Sediment-Water Interface to Coherent Turbulent Motions

Abstract

Unique observations of the hydrodynamics across the sediment-water interface are used to quantify the instantaneous response of the interstitial fluid to the passage of coherent turbulent motions in the overlying flow. Over a range of permeability Reynolds numbers ReK=√Ku∗/ν (where K is the sediment permeability, u∗ is the shear velocity, and ν is the fluid viscosity), the passage of these turbulent motions create velocity fluctuations and momentum fluxes at the sediment-water interface to greatly exceed their mean values. Sweep motions are observed to penetrate into the sediment bed and induce instantaneous momentum fluxes that can be an order of magnitude larger than the mean bed shear str..