Experimental study on flow and sediment distribution at off-take channel

Abstract

River off-take is one of the complex features in fluvial systems and the distribution of flow, and sediments along the branches are still a matter of research. This paper deals with a physical simulation on an off-take channel for understanding the flow and sediment distribution in the vicinity. Laboratory-based test runs have been carried out by changing the discharges and the angles off-take. A total of eighteen test runs have been conducted for three discharge conditions with three off-take angles. Two equations for predicting water and sediment discharge ratios have been proposed as a function of Froude number, channel geometry and off-take angel. Flow visualizations have also been carried out in the vicinity of the off-take for understanding erosion and sedimentation pattern. Flow and sediment movement patterns were carefully observed during the simulation and four distinguished zone formations have been noted in the vicinity. Finally, validations of the developed equations have been done with the field data from selected river off-take systems of Bangladesh. Validation results of field data show mean discrepancy ratios of 0.83 for the discharge equation and 0.89 for sediment equation during low flow.