Length and Time Scales of Response of Sediment Suspensions to Changing Flow Conditions

Robert M. Dorrell, Andrew J. Hogg*

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

19 Citations (Scopus)

Abstract

Turbulent suspensions of sediment are investigated to establish the characteristic length and time scales on which they adjust from one state to another. The suspensions are modeled by using a simple closure for the turbulent fluctuations in which the average flux of sediment is treated as a diffusion process. A key dimensionless settling parameter, which is closely related to the Rouse number, measures the magnitude of the settling to diffusive fluxes of particles. It is shown how the length and time scales on which the suspension responds are a function of the settling parameter and the assumed form of the eddy diffusivity, and that the predictions are broadly in accord with laboratory experiments. It is further established analytically that, in the regimes of the settling parameter much greater or much less than unity, the timescale of response is independent of the form of the eddy diffusivity. This motivates the use of simple eddy diffusivity laws to provide generic insight to the unsteady evolution of complex suspension and sedimentation problems.

Original languageEnglish
Pages (from-to)430-439
Number of pages10
JournalJournal of Hydraulic Engineering
Volume138
Issue number5
DOIs
Publication statusPublished - 10 May 2012

Keywords

  • Eddy diffusivity
  • Flow boundary conditions
  • Sedimentation
  • Suspended sediment concentration
  • Timescale of response

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