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Inadequacy of fluvial energetics for describing gravity current autosuspension
Sojiro Fukuda1, Marijke G W de Vet2, Edward W G Skevington2
1Energy and Environment Institute, University of Hull, Hull, UK. S.Fukuda-2018@hull.ac.uk.
Nature Communications
|April 21, 2023
Summary
Material transport in gravity currents, like turbidity currents, differs fundamentally from river flows. Enhanced mixing efficiency is observed due to a non-linear relationship between buoyancy and flow power.
Area of Science:
- Fluid dynamics
- Geophysics
- Sediment transport
Background:
- Gravity currents, including turbidity currents, are density-driven flows crucial in natural systems.
- Current models often assume dynamic similarity between gravity currents and fluvial flows for material transport.
- The long run-out and driving mechanisms of turbidity currents remain incompletely understood.
Purpose of the Study:
- To investigate the fundamental differences in material transport between particle-driven gravity currents and fluvial systems.
- To challenge the assumption of dynamic similarity in existing gravity current models.
- To revise the energy budget of gravity currents based on empirical and experimental data.
Main Methods:
- Integration of empirical research from various particle-driven gravity currents.
- Inclusion of new experimental data on gravity current dynamics.
- Analysis of energy budgets and buoyancy production in these flows.
Main Results:
- Material transport in gravity currents is shown to be fundamentally different from fluvial systems.
- Buoyancy production exhibits a non-linear dependence on available flow power, contrary to current theories.
- This indicates an underestimation of kinetic energy loss from the mean flow in existing models.
Conclusions:
- The mixing efficiency of gravity currents is enhanced.
- Revised energy budget calculations support the observed enhancement in mixing.
- Findings necessitate a re-evaluation of current models for gravity current dynamics and sediment transport.
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