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Parameterization of near-bed processes under collinear wave and current flows from a two-phase sheet flow model

Amoudry, Laurent O; Liu, Philip L.-F. 2010 Parameterization of near-bed processes under collinear wave and current flows from a two-phase sheet flow model. Continental Shelf Research, 30 (13). 1403-1416. 10.1016/j.csr.2010.04.009

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Abstract/Summary

Sediment transport models require appropriate representation of near-bed processes. We aim here to explore the parameterizations of bed shear stress, bed load transport rate and near-bed sediment erosion rate under the sheet flow regime. To that end, we employ a one-dimensional two-phase sheet flow model which is able to resolve the intrawave boundary layer and sediment dynamics at a length scale on the order of the sediment grain. We have conducted 79 numerical simulations to cover a range of collinear wave and current conditions and sediment diameters in the range 210–460 μm. The numerical results confirm that the intrawave bed shear stress leads the free stream velocity, and we assess an explicit expression relating the phase lead to the maximum velocity, wave period and bed roughness. The numerical sheet flow model is also used to provide estimates for the bed load transport rate and to inspect the near-bed sediment erosion. A common bed load transport rate formulation and two typical reference concentration approaches are assessed. A dependence of the bed load transport rate on the sediment grain diameter is observed and parameterized. Finally, the intrawave near-bed vertical sediment flux is further investigated and related to the time derivative of the bed shear stress.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1016/j.csr.2010.04.009
Programmes: Oceans 2025 > Shelf and coastal processes
POL Programmes > Shallow coastal seas - function and impacts of change > Process experiments at small scale
ISSN: 0278-4343
Additional Keywords: SEDIMENT TRANSPORT MODELLING; SHEET FLOWS; SEDIMENT EROSION; BED LOAD; TRANSPORT RATE; BOUNDARY LAYER
NORA Subject Terms: Marine Sciences
Date made live: 21 Jul 2010 10:06
URI: http://nora.nerc.ac.uk/id/eprint/9950

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