Inadequacy of fluvial energetics for describing gravity current autosuspension

TL;DR

This paper demonstrates that traditional fluvial-based models are inadequate for describing gravity current dynamics, revealing nonlinear buoyancy production and increased mixing efficiency through empirical and experimental analysis.

Contribution

It introduces a revised energy budget showing that gravity currents differ fundamentally from fluvial flows, challenging existing models.

Findings

Buoyancy production has a nonlinear dependence on flow power.

Gravity currents exhibit higher mixing efficiency than previously thought.

Material transport in gravity currents is fundamentally different from fluvial systems.

Abstract

"Consider the [turbidity] current as ... a river" R. A. Bagnold (1962); the foundation of contemporary deep marine sedimentology. Gravity currents, such as sediment-laden turbidity currents, are ubiquitous natural flows that are driven by a density difference. Turbidity currents have provided vital motivation to advance understanding of this class of flows because their enigmatic long run-out and driving mechanisms are not properly understood. Extant models assume that material transport by gravity currents is dynamically similar to fluvial flows. Here, empirical research from different types of particle-driven gravity currents is integrated with our experimental data, to show that material transport is fundamentally different from fluvial systems. Contrary to current theory, buoyancy production is shown to have a non-linear dependence on available flow power, indicating an underestimation of the total kinetic energy lost from the mean flow. A revised energy budget directly implies that the mixing efficiency of gravity currents is enhanced.