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Gravity currents from moving sources

Published online by Cambridge University Press:  17 August 2021

Raphael Ouillon Open the ORCID record for Raphael Ouillon [Opens in a new window] ,
Christos Kakoutas ,
Eckart Meiburg Open the ORCID record for Eckart Meiburg [Opens in a new window]  and
Thomas Peacock Open the ORCID record for Thomas Peacock [Opens in a new window]
Raphael Ouillon*
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
Christos Kakoutas
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
Eckart Meiburg
Affiliation:
Department of Mechanical Engineering, University of California at Santa Barbara, Santa Barbara, CA 93106, USA
Thomas Peacock
Affiliation:
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA 02139, USA
*
†Email address for correspondence: ouillon@mit.edu
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Abstract

Emerging technologies such as deep-sea mining and geoengineering pose fundamentally new questions regarding the dynamics of gravity currents. Such activities can continuously release dense sediment plumes from moving locations, thereafter propagating as gravity currents. Here, we present the results of idealized numerical simulations of this novel configuration, and investigate the propagation of a gravity current that results from a moving source of buoyancy, as a function of the ratio of source speed to buoyancy velocity. We show that above a certain value of this ratio, the flow enters a supercritical regime in which the source moves more rapidly than the generated current, resulting in a statistically steady state in the reference frame of the moving source. Once in the supercritical regime, the current goes through a second transition beyond which fluid in the head of the current moves approximately in the direction normal to the direction of motion of the source, and the time evolution of the front in the lateral direction is well described by an equivalent constant volume lock-release gravity current. We use our findings to gain insight into the propagation of sediment plumes released by deep-sea mining collector vehicles, and present proof-of-concept tow-tank laboratory experiments of a model deep-sea mining collector discharging dense dyed fluid in its wake. The experiments reveal the formation a wedge-shaped gravity current front which narrows as the ratio of collector-to-buoyancy velocity increases. The time-averaged front position shows good agreement with the results of the numerical model in the supercritical regime.

JFM classification

Geophysical and Geological Flows: Gravity currents Geophysical and Geological Flows: Stratified flows
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 924 , 10 October 2021 , A43
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Copyright
© The Author(s), 2021. Published by Cambridge University Press

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References

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Ouillon et al. supplementary movie

Video of the tow-tank experiment at $a=1.11$ showing the gravity current behaviour of the dense dyed fluid being released from the back of a model deep sea mining collector via a discharge pipe.

Download Ouillon et al. supplementary movie(Video)
Video 10.5 MB