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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Spatial variability of three-dimensional Reynolds stresses in a developing channel bend
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Spatial variability of three-dimensional Reynolds stresses in a developing channel bend

机译：发展中的河道弯道中三维雷诺应力的空间变异性

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摘要

Experimental results of the mean flow field and turbulence characteristics for flow in a model channel bend with a mobile sand bed are presented. Acoustic Doppler velocimeters (ADVs) were used to measure the three components of instantaneous velocities at multiple cross sections in a 135° channel bend for two separate experiments at different stages of clear water scour conditions. With measurements at multiple cross sections through the bend it was possible to map the changes in both the spatial distribution of the mean velocity field and the three Reynolds shear stresses. Turbulent stresses are known to contribute to sediment transport and the three-dimensionality inherent to flow in open channel bends presents a useful case for determining specific relations between three-dimensional turbulence and sediment entrainment and transport. These measurements will also provide the necessary data for validating numerical simulations of turbulent flow and sediment transport. The results show that the magnitude and distribution of three-dimensional Reynolds stresses increase through the bend, with streamwise-cross stream and cross stream-vertical components exceeding the maximum principal Reynolds stress through the bend. The most intriguing observation is that near-bed maximum positive streamwise-cross stream Reynolds stress coincides with the leading edge of the outer bank scour hole (or thalweg), while maximum cross stream-vertical Reynolds stress (in combination with high negative streamwise-cross stream Reynolds stress near the bend apex) coincides with the leading edge of the inner bank bar. Maximum Reynolds stress and average turbulent kinetic energy appear to be greater and more localized over the scour hole before final equilibrium scour is reached. This suggests that the turbulent energy in the flow is higher while the channel bed is developing, and both lower turbulent energy and a broader distribution of turbulent stresses near the bed are required for cessation of particle mobilization and transport.
机译：给出了带有移动沙床的模型通道弯道的平均流场和湍流特性的实验结果。声学多普勒测速仪（ADV）用于在135°通道弯道中的多个横截面上测量瞬时速度的三个分量，用于在清水冲刷条件不同阶段进行两个单独的实验。通过对弯曲处的多个横截面进行测量，可以绘制平均速度场的空间分布和三个雷诺剪切应力的变化。众所周知，湍流应力有助于沉积物的输送，明渠弯道中水流固有的三维性为确定三维湍流与泥沙夹带和输送之间的特定关系提供了一个有用的案例。这些测量结果还将提供必要的数据，以验证湍流和泥沙输送的数值模拟。结果表明，三维雷诺应力的大小和分布在弯曲处增加，流向横向流和横向流的垂直分量超过了弯曲处的最大主雷诺应力。最有趣的观察结果是，近床层最大顺流横流雷诺应力与外岸冲刷孔（或thalweg）的前缘重合，而最大横流垂直雷诺应力（与高负向流横贯相结合）弯曲顶点附近的流雷诺应力与内堤坝的前缘重合。在达到最终平衡冲刷之前，最大雷诺应力和平均湍动能似乎更大且更多地位于冲刷孔上方。这表明，在通道床不断发展的同时，流中的湍流能更高，并且为了停止颗粒的动员和运输，较低的湍流能和靠近床层的湍流应力分布都需要。

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