Turbulence Processes Within Turbidity Currents

Abstract

Sediment-laden gravity currents, or turbidity currents, are density-driven flows that transport vast quantities of particulate material across the floor of lakes and oceans. Turbidity currents are generated by slope failure or initiated when a sediment-laden flow enters into a lake or ocean; here, lofting or convective sedimentation processes may control flow dynamics. Depending upon the internal turbulent mixing, which keeps particles in suspension, turbidity currents can travel for thousands of kilometers across the seafloor. However, despite several competing theories, the process for the ultralong runout of these flows remains enigmatic. Turbidity currents often generate large sinuous channel–levee systems, and the dynamics of how turbidity currents flow around channel bends are strongly influenced by internal density and velocity structure, with large-scale flows being modified by the Coriolis force. Therefore, understanding some of the largest sedimentary structures on the Earth's surface depends on the turbulence processes within turbidity currents. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 53 is January 7, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Sedimentary processes at the mouth of a tidally‐influenced delta: New insights from submarine observatory measurements, Fraser Delta, Canada

“…However, removal rates of fine sediment from hypopycnal plumes are typically much greater than predicted using Stokes settling velocities, thus requiring the use of empirical relationships in numerical models (Morehead & Syvitski, 1999). Whereas increased removal rates have been attributed to flocculation (Hill & Nowell, 1995;Hill et al, 2000), laboratory studies have brought to light convective sedimentation mechanisms, whereby a high sediment concentration gradient at the interface between the buoyant low salinity plume and underlying saline marine water causes gravitational instability (Maxworthy, 1999;Parsons et al, 2001;Wells & Dorrell, 2021). Because these processes provide a mechanism for rapidly increasing concentrations of sediment, an important implication is that bottom hyperpycnal densities can be generated from considerably lower hypopycnal plume concentrations and by a much larger range of rivers than previously thought (Mulder & Syvitski, 1995).…”

Experimental Insights on the Propagation of Fine‐Grained Geophysical Flows Entering Water

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