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Toward representing wave-induced sediment suspension over sand ripples in RANS models

Amoudry, Laurent; Bell, Paul; Thorne, Peter; Souza, Alejandro. 2013 Toward representing wave-induced sediment suspension over sand ripples in RANS models. Journal of Geophysical Research: Oceans, 118 (5). 2378-2392. 10.1002/jgrc.20188

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Abstract/Summary

Parameterizations of near-bed sediment processes are commonly associated with the poor predictive skill of coastal sediment transport models. We implement a two-dimensional Reynolds-averaged Navier-Stokes model to directly assess these parameterizations by reproducing measurements obtained in large-scale wave flume experiments. A sediment transport model has been coupled to wave hydrodynamics and turbulence, and numerical experiments provide temporal and spatial variations of free surface, flow velocity, sediment concentration, and turbulence quantities. Model-data comparisons enable the direct assessment of how key suspension processes are represented and of the inherent variability of the sediment transport model. We focus on the different processes occurring above rippled beds versus dynamically flat beds. Numerical results show that increasing roughness alone is not sufficient to have good predictive capability above steep ripples. Some parameterization of the vortex entrainment process is necessary and a simple modification, which leads to constant sediment diffusivity above steep-rippled beds, is sufficient to obtain good predictions of wave-averaged suspended concentrations. Model-data comparisons for the turbulent kinetic energy are also presented and highlight the need to account for the effect of vortex entrainment on near-bed turbulence and transfer of momentum.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1002/jgrc.20188
Programmes: NOC Programmes > Marine Physics and Ocean Climate
ISSN: 2169-9291
Additional Keywords: sediment transport; ripples; RANS modelling; turbulence
Date made live: 25 Apr 2013 09:34 +0 (UTC)
URI: http://nora.nerc.ac.uk/id/eprint/501471

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