Experimental Study On The Flow Structure And Bed Forms In Open-Channel Bends

Water resources are closely related with human life. In recent years, series of achievements have been made in many fields of hydraulics. Meanwhile, a further acknowledge of 3-d flow structure, the characteristics of flow turbulence and river morphology is still necessary, otherwise it will bring us difficulties in prediction of riverbed evolution and reply to emergencies. Thus, it is of great importance to do in-depth research in hydrodynamic characteristics and riverbed morphology. The research would be conducted in interior open flume due to difficulties existed in obtaining measured data with expensive cost and low precision.The experimental flume is composed of a 180 degree bend flume and two straight ones. The instantaneous velocities in three directions of each measuring point are measured by the Acoustic Doppler Velocimeter. The paper has analyzed the average velocities in flow direction, velocity contour maps, the power axis of flow, flow velocity distributions along the vertical direction and circulation flow in river bends, laid a foundation for the research of continuous curves in natural rivers.Flow movements and sediment transport would cause changes in river bed forms, which exerts vital influence on river evolution. It makes sense to predict river morphology grounded on the conditions of flow and sediment transportation. Flow would compliance with the law of resistance during its travelling, while the resistance encountered would change with flow and sediment conditions. As a result, it would have an impact on river channel process.Based on the law of resistance and the existing flume experimental data, two dimensionless bed form parameters, as well as the boundaries between various bed forms are proposed. Different river morphology is demonstrated in the distribution diagram, which could be used in both high and low flow regimes. The correspondence between morphological parameters and different bed form configurations is analyzed. The boundary equations between different bed forms, as well as high and low flow regimes, are obtained in accordance with the research of morphological parameters. All these results show that the method is able to discriminate bed forms in different flow regimes.