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A novel mixing mechanism in sinuous seafloor channels: Implications for submarine channel evolution

Dorrell, R. M.; Peakall, J.; Burns, C.; Keevil, G. M.

Abstract

Previous experimental studies of density currents in sinuous seafloor channels have almost exclusively studied hydrodynamics either by considering time independent, instantaneous, flow measurements or by compiling time-averaged flow measurements. Here we present a novel study of the time dependent dynamics of a density driven flow in a sinuous channel fed by a source of constant discharge. The experiments show that whilst source conditions may be temporally steady, flow conditions are temporally unsteady with timescales of flow variation driven by flow interaction with channel topography. Temporal variations reveal that both downstream and cross-stream flows vary significantly from time average observations and predictions, across scales larger than those predicted for turbulence in equivalent straight channels. Large-scale variations are shown to increase the average production of turbulence across the height of the flow, providing a new mechanism for enhanced mixing of sediment within gravity currents. Further such large-scale variations in flow conditions are recorded in the change in orientation of near-bed secondary flow, providing a plausible mechanism to reduce the cross-stream transport of bedload material and explain the ultimate stabilisation of sinuous seafloor channel systems.

Journal Article Type Article
Publication Date Feb 15, 2018
Journal Geomorphology
Print ISSN 0169-555X
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 303
Pages 1-12
DOI https://doi.org/10.1016/j.geomorph.2017.11.008
Keywords Turbidity current; Sinuous channel; Secondary flow; Mixing
Copyright Statement © 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/

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Copyright Statement
© 2018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/



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