BED LOAD TRANSPORT OF FINE SAND BY LAMINAR AND TURBULENT FLOW

Anthony J. Grass, Ragaei N.M. Ayoub

Abstract


An experimental study is described in which the rate of transport of fine sand over a flat bed was measured as a function of the shear stress exerted on the bed by both laminar and turbulent flows, for a range of water temperatures. The results confirm the great sensitivity of the transport rate to changes in both shear stress and temperature over the test range. The hypothesis is propounded that in certain specified circumstances, the net rate of local bed load transport generated by an arbitrary unsteady flow, can be estimated by integration, using the measured steady laminar flow transport relationships in conjunction with the time history or probability distribution of the fluctuating bed shear stress. The concept has been tested using the measured data with encouraging results. It is suggested that this method of linking the characteristics of the near bed flow field to the local induced rates of sediment transport could be productively applied in a range of studies including the initiation and development of bed sand ripples by the action of various combinations of waves and steady currents.

Keywords


bed load; bed transport; fine sand; laminar flow; turbulent flow

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