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Theoretical impulse threshold for particle dislodgement

Theoretical impulse threshold for particle dislodgement
Theoretical impulse threshold for particle dislodgement
The problem of determining the threshold of motion of a sediment particle resting on the bed of an open channel has historically been dominated by an approach based on the time-space-averaged bed shear stress (i.e. Shields criterion). Recently, experimental studies have promoted an alternative approach to predict the dislodgement threshold, which is based on the impulse of the flow-induced force. Nonetheless, theoretical analyses accompanying these studies result in complex expressions that fail to provide a direct estimate of said impulse threshold. We employ the work-energy principle to derive a prediction of the fundamental impulse threshold that the destabilising hydrodynamic force must overcome in order to achieve full particle dislodgement. For the bed configuration studied, which is composed of spheres, the proposed expression depends on the mobile particle's size and mass, and shows excellent agreement with experimental observations previously published. The derivation presented in this paper may thus represent a robust theoretical framework that aids in the re-interpretation of existing data, as well as in the design of future experiments aimed at analysing the importance of hydrodynamic impulse as a criterion for prediction of particle dislodgement.
0022-1120
893-903
Maldonado-Villanueva, Sergio
b303ef8c-52d6-40ed-bf48-59efb4265a85
De Almeida, Gustavo
f6edffc1-7bb3-443f-8829-e471b6514a7e
Maldonado-Villanueva, Sergio
b303ef8c-52d6-40ed-bf48-59efb4265a85
De Almeida, Gustavo
f6edffc1-7bb3-443f-8829-e471b6514a7e

Maldonado-Villanueva, Sergio and De Almeida, Gustavo (2019) Theoretical impulse threshold for particle dislodgement. Journal of Fluid Mechanics, 863, 893-903. (doi:10.1017/jfm.2018.996).

Record type: Article

Abstract

The problem of determining the threshold of motion of a sediment particle resting on the bed of an open channel has historically been dominated by an approach based on the time-space-averaged bed shear stress (i.e. Shields criterion). Recently, experimental studies have promoted an alternative approach to predict the dislodgement threshold, which is based on the impulse of the flow-induced force. Nonetheless, theoretical analyses accompanying these studies result in complex expressions that fail to provide a direct estimate of said impulse threshold. We employ the work-energy principle to derive a prediction of the fundamental impulse threshold that the destabilising hydrodynamic force must overcome in order to achieve full particle dislodgement. For the bed configuration studied, which is composed of spheres, the proposed expression depends on the mobile particle's size and mass, and shows excellent agreement with experimental observations previously published. The derivation presented in this paper may thus represent a robust theoretical framework that aids in the re-interpretation of existing data, as well as in the design of future experiments aimed at analysing the importance of hydrodynamic impulse as a criterion for prediction of particle dislodgement.

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Accepted/In Press date: 3 December 2018
e-pub ahead of print date: 28 January 2019
Published date: 25 March 2019

Identifiers

Local EPrints ID: 426663
URI: https://eprints.soton.ac.uk/id/eprint/426663
ISSN: 0022-1120
PURE UUID: 5fadd889-e542-462e-8bdd-e3aed9960cad
ORCID for Gustavo De Almeida: ORCID iD orcid.org/0000-0002-3291-3985

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Date deposited: 10 Dec 2018 17:30
Last modified: 23 Apr 2019 00:30

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