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Quasi-two-layer morphodynamic model for bedload-dominated problems: bed slope-induced morphological diffusion

Quasi-two-layer morphodynamic model for bedload-dominated problems: bed slope-induced morphological diffusion
Quasi-two-layer morphodynamic model for bedload-dominated problems: bed slope-induced morphological diffusion
We derive a two-layer depth-averaged model of sediment transport and morphological evolution for application to bedload-dominated problems. The near-bed transport region is represented by the lower (bedload) layer which has an arbitrarily constant, vanishing thickness (of approx. 10 times the sediment particle diameter), and whose average sediment concentration is free to vary. Sediment is allowed to enter the upper layer, and hence the total load may also be simulated, provided that concentrations of suspended sediment remain low. The model conforms with established theories of bedload, and is validated satisfactorily against empirical expressions for sediment transport rates and the morphodynamic experiment of a migrating mining pit by Lee et al. (1993 J. Hydraul. Eng. 119, 64–80 (doi:10.1061/(ASCE)0733-9429(1993)119:1(64))). Investigation into the effect of a local bed gradient on bedload leads to derivation of an analytical, physically meaningful expression for morphological diffusion induced by a non-zero local bed slope. Incorporation of the proposed morphological diffusion into a conventional morphodynamic model (defined as a coupling between the shallow water equations, Exner equation and an empirical formula for bedload) improves model predictions when applied to the evolution of a mining pit, without the need either to resort to special numerical treatment of the equations or to use additional tuning parameters.
1-19
Maldonado, Sergio
b303ef8c-52d6-40ed-bf48-59efb4265a85
Borthwick, Alistair
20792d04-a4e5-4e3d-8ba6-26e47128dd81
Maldonado, Sergio
b303ef8c-52d6-40ed-bf48-59efb4265a85
Borthwick, Alistair
20792d04-a4e5-4e3d-8ba6-26e47128dd81

Maldonado, Sergio and Borthwick, Alistair (2018) Quasi-two-layer morphodynamic model for bedload-dominated problems: bed slope-induced morphological diffusion. Royal Society Open Science, 5, 1-19. (doi:10.1098/rsos.172018).

Record type: Article

Abstract

We derive a two-layer depth-averaged model of sediment transport and morphological evolution for application to bedload-dominated problems. The near-bed transport region is represented by the lower (bedload) layer which has an arbitrarily constant, vanishing thickness (of approx. 10 times the sediment particle diameter), and whose average sediment concentration is free to vary. Sediment is allowed to enter the upper layer, and hence the total load may also be simulated, provided that concentrations of suspended sediment remain low. The model conforms with established theories of bedload, and is validated satisfactorily against empirical expressions for sediment transport rates and the morphodynamic experiment of a migrating mining pit by Lee et al. (1993 J. Hydraul. Eng. 119, 64–80 (doi:10.1061/(ASCE)0733-9429(1993)119:1(64))). Investigation into the effect of a local bed gradient on bedload leads to derivation of an analytical, physically meaningful expression for morphological diffusion induced by a non-zero local bed slope. Incorporation of the proposed morphological diffusion into a conventional morphodynamic model (defined as a coupling between the shallow water equations, Exner equation and an empirical formula for bedload) improves model predictions when applied to the evolution of a mining pit, without the need either to resort to special numerical treatment of the equations or to use additional tuning parameters.

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Accepted/In Press date: 19 January 2018
e-pub ahead of print date: 28 February 2018
Published date: February 2018

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Local EPrints ID: 418475
URI: https://eprints.soton.ac.uk/id/eprint/418475
PURE UUID: 0a4faad4-2aa4-4a55-91a9-6210f3959937

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Date deposited: 09 Mar 2018 17:30
Last modified: 09 Dec 2019 18:19

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