Particle settling from constant-flux surface gravity currents and a near-stationary particle-bearing layer

Bruce R. Sutherland, Brianna Mueller, Brendan Sjerve, and David Deepwell
Phys. Rev. Fluids 6, 063802 – Published 10 June 2021

Abstract

Experiments are performed examining particle settling from constant-flux surface gravity currents and from a near-stationary layer of particle-bearing fluid overlying a saline ambient fluid. The particles consisted either of clay or of near-spherical glass ballotini with four different mean diameters. In the case of ballotini with relatively large diameters (46μm), the particles formed a settling front within the current the settling speed of which was consistent with the Stokes settling velocity for a single particle. A single particle plume descended below the current over the extent of the settling front. In the case of clay and of 6μm diameter ballotini, no settling within or below the current was observed before the current nose reached the end of the tank and the source was turned off. After a time on the order of minutes, these particles were found to descend from the near-stationary surface layer through convective instability, though this may have been preconditioned by a fingering instability in the stratified interface between the upper and lower layers. Even though the particle concentration in the current and upper layer was less than 0.5% in all experiments, the front of the particle plumes descended at significantly greater speeds than the settling velocity of an individual particle. The relative descent speed was larger for smaller particles, with clay, in particular, descending at a speed on the order of 1000 times that of an individual clay particle.

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  • Received 17 March 2021
  • Accepted 27 May 2021

DOI:https://doi.org/10.1103/PhysRevFluids.6.063802

©2021 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Bruce R. Sutherland1,2,*, Brianna Mueller1, Brendan Sjerve3, and David Deepwell1

  • 1Department of Physics, University of Alberta, Edmonton, AB, Canada T6G 2E1
  • 2Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E3
  • 3Department of Mechanical Engineering, University of Alberta, Edmonton, AB, Canada T6G 1H9

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Vol. 6, Iss. 6 — June 2021

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