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The Hydrodynamic Response of the Sediment‐Water Interface to Coherent Turbulent Motions
Author(s) -
Voermans Joey J.,
Ghisalberti Marco,
Ivey Gregory N.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl079850
Subject(s) - turbulence , geology , sediment , shear velocity , shear stress , mechanics , reynolds stress , reynolds number , flow velocity , mean flow , hyperconcentrated flow , flow (mathematics) , permeability (electromagnetism) , geotechnical engineering , sediment transport , geomorphology , physics , bed load , chemistry , biochemistry , membrane
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 R e K = K u ∗ / 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 stress. By penetrating into the sediment bed, the turbulent motions increase the effective roughness experienced by the flow and therefore the flow resistance. The properties of the mean flow alone are thus insufficient to describe the interaction of the overlying flow with the sediments.