Articles | Volume 5, issue 3
https://doi.org/10.5194/esurf-5-399-2017
https://doi.org/10.5194/esurf-5-399-2017
Research article
 | 
19 Jul 2017
Research article |  | 19 Jul 2017

The influence of turbulent bursting on sediment resuspension under unidirectional currents

Sarik Salim, Charitha Pattiaratchi, Rafael Tinoco, Giovanni Coco, Yasha Hetzel, Sarath Wijeratne, and Ravindra Jayaratne

Abstract. Laboratory experiments were conducted in an open channel flume with a flat sandy bed to examine the role of turbulence on sediment resuspension. An acoustic Doppler velocimeter (ADV) was used to measure the instantaneous three-dimensional velocity components and acoustic backscatter as a proxy to suspended sediment concentration. Estimates of sediment transport assume that there is a mean critical velocity that needs to be exceeded before sediment transport is initiated. This approach does not consider the turbulent flow field that may initiate sediment resuspension through event-based processes such as the bursting phenomenon. In this paper, laboratory measurements were used to examine the sediment resuspension processes below and above the mean critical velocity. The results within a range above and below the measured mean critical velocity suggested that (1) the contribution of turbulent bursting events remained identical in both experimental conditions, (2) ejection and sweep events contributed more to the total sediment flux than up-acceleration and down-deceleration events, and (3) wavelet transform revealed a correlation between the momentum and sediment flux in both test conditions. Such similarities in conditions above and below the measured mean critical velocity highlight the need to re-evaluate the accuracy of a single time-averaged mean critical velocity for the initiation of sediment entrainment.

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Short summary
The aim of this paper was to verify the existence of a mean critical velocity concept in terms of turbulent bursting phenomena. Laboratory experiments were undertaken in a unidirectional current flume where an acoustic Doppler velocimeter was used. Results in the laboratory conditions both above and below the measured mean critical velocity highlighted the need to re-evaluate the accuracy of a single time-averaged critical velocity for the initiation of sediment entrainment.