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Theoretical models for the formation and development of sand and gravel waves

Theoretical models for the formation and development of sand and gravel waves
Theoretical models for the formation and development of sand and gravel waves

A two dimensional stability analysis is carried out of flow of low Froude number over an erodible bed. The closure of the equations of motion is made at the level of the turbulent energy equation. Two separate modes of instability occur with wavelengths related to the roughness of the bed and the depth of flow. It i s postulated that these two modes correspond to the formation of ripples and dunes respectively.To study the flow above finite amplitude sand waves a non-linear numerical model is developed. By making use of a non-orthogonal mapping of the coordinate system the resulting equations are solved numerically using finite difference techniques. The effects of changes in the wave amplitude, shape and surface roughness are considered. The present results are restricted to flow of low Froude number. The implications of the model for the transport of sediment over the wave and the resulting change in the bed form are examined by relating the bedload transport to the bed shear stress. Computations are made for the flow above sand waves with profiles similar in shape to observed waves in river and sea environments.

University of Southampton
Richards, Kelvin John
Richards, Kelvin John

Richards, Kelvin John (1978) Theoretical models for the formation and development of sand and gravel waves. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

A two dimensional stability analysis is carried out of flow of low Froude number over an erodible bed. The closure of the equations of motion is made at the level of the turbulent energy equation. Two separate modes of instability occur with wavelengths related to the roughness of the bed and the depth of flow. It i s postulated that these two modes correspond to the formation of ripples and dunes respectively.To study the flow above finite amplitude sand waves a non-linear numerical model is developed. By making use of a non-orthogonal mapping of the coordinate system the resulting equations are solved numerically using finite difference techniques. The effects of changes in the wave amplitude, shape and surface roughness are considered. The present results are restricted to flow of low Froude number. The implications of the model for the transport of sediment over the wave and the resulting change in the bed form are examined by relating the bedload transport to the bed shear stress. Computations are made for the flow above sand waves with profiles similar in shape to observed waves in river and sea environments.

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Published date: 1978

Identifiers

Local EPrints ID: 458386
URI: http://eprints.soton.ac.uk/id/eprint/458386
PURE UUID: 5fa040f9-4239-42f5-a99d-4117f62744e9

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Date deposited: 04 Jul 2022 16:48
Last modified: 04 Jul 2022 16:48

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Contributors

Author: Kelvin John Richards

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