Modulation of time-mean and turbulent flow by suspended sediment

Hadis Matinpour, Sean Bennett, Joseph Atkinson, and Michele Guala
Phys. Rev. Fluids 4, 074605 – Published 25 July 2019

Abstract

Nearly all geophysical flows entrain, transport, and deposit sediment, and many studies have sought to define how the presence of suspended sediment can affect flow dynamics of the carrier fluid. Yet the mechanisms of turbulence modulation by suspended sediment remain poorly understood. Experiments were conducted in a mixing box to evaluate the effects of suspended sand on the turbulent flow generated by an oscillating grid placed near the bottom of the box. Two-phase particle image velocimetry was used to obtain velocity characteristics of the sediment and fluid phases separately. Boundary conditions included a clear-water flow and six sediment-laden flows for comparative purposes. A strong secondary circulation was observed within the mixing box due to the position of the grid and stroke length. As sediment loading increased, the depth affected by the secondary circulation, the mean and turbulent kinetic energy, and the total suspended-sediment concentration decreased while turbulent length scales increased. These features coincided with the formation of a stratified layer where high suspended-sediment concentration occurred. Key length scales related to the vertical extent of secondary circulation regions, vertical mixing, and maxima of suspended-sediment concentrations were defined and used to identify and explain the formation of this stratified layer and the modulation of flow. The results presented here demonstrate the marked effects that suspended sediment and the formation of a stratified layer have on turbulent flow dynamics within a mixing box, and these results are expected to have broader implications for the study and interpretation of a wide range of sediment-laden geophysical flows.

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  • Received 18 October 2018

DOI:https://doi.org/10.1103/PhysRevFluids.4.074605

©2019 American Physical Society

Physics Subject Headings (PhySH)

Fluid Dynamics

Authors & Affiliations

Hadis Matinpour1,*, Sean Bennett2, Joseph Atkinson1, and Michele Guala3

  • 1Department of Civil, Structural and Environmental Engineering, University at Buffalo, Buffalo, New York 14228, USA
  • 2Department of Geography, University at Buffalo, Buffalo, New York 14261, USA
  • 3St. Anthony Falls Laboratory and Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, Minnesota 55455, USA

  • *hadismat@buffalo.edu

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Vol. 4, Iss. 7 — July 2019

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