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.

Citation

Dorrell, R. M., Peakall, J., Burns, C., & Keevil, G. M. (2018). A novel mixing mechanism in sinuous seafloor channels: Implications for submarine channel evolution. Geomorphology, 303, 1-12. https://doi.org/10.1016/j.geomorph.2017.11.008

• Journal Article Type: Article
• Acceptance Date: Nov 14, 2017
• Online Publication Date: Nov 21, 2017
• Publication Date: Feb 15, 2018
• Deposit Date: Jan 2, 2018
• Publicly Available Date: Nov 22, 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
• Public URL: https://hull-repository.worktribe.com/output/475526
• Contract Date: Jan 2, 2018