ABSTRACT The present paper concerns an experimental study of externally generated turbulence and its impact on the bed load sediment transport in an open channel flow. The external turbulence was generated by vertically oscillating a submerged grid, hereafter referred to as turbulence generator, in the flume with a clearance of 11 cm from the bed. Two kinds of experiments were performed: rigid flat-bed and plane sand-bed. One two-dimensional (2-D) LDA was set up to measure the velocity profiles for different values of flow discharge, amplitude and period of oscillations of the turbulence generator. The mean velocities, turbulence intensities, Reynolds shear stress, and their impacts on the rate of sediment transport have been analyzed. The fractional contributions of burst-sweep cycles to the Reynolds shear stress have also been studied. The turbulence generated due to a vertically oscillating-submerged grid is an analogous to the production of turbulence beneath the roller located on the front of broken wave, and the impact thus lies on the sediment transport. The Shields parameter was found to be correlated with the sediment transport rate, and the transport rate as a function of turbulence level is found to increase with turbulence level.

中文翻译：

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垂直振荡网格板产生的外部湍流及其对泥沙输运速率的影响

摘要 本文涉及外部产生湍流的实验研究及其对明渠流中床载沉积物输送的影响。外部湍流是通过在距床 11 厘米的水槽中垂直振荡浸入式网格（以下称为湍流发生器）而产生的。进行了两种试验：刚性平床和平面砂床。建立了一个二维 (2-D) LDA 来测量湍流发生器的不同流量值、振幅和振荡周期的速度分布。分析了平均速度、湍流强度、雷诺剪切应力及其对沉积物输送速率的影响。还研究了爆破-扫描循环对雷诺剪切应力的部分贡献。垂直振荡-淹没网格产生的湍流类似于位于破碎波前端的滚筒下方产生的湍流，因此影响泥沙输运。发现 Shields 参数与沉积物传输速率相关，并且发现作为湍流水平的函数的传输速率随着湍流水平而增加。