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首页> 外文期刊>KSCE journal of civil engineering >An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress
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An experimental study of mean and turbulent flow in a 180 degree sharp open channel bend: Secondary flow and bed shear stress

机译：180度明渠弯曲中平均和湍流的实验研究：二次流和床切应力

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High flow velocity near the free surface in rivers is due to the presence of shear stress near the bed and its absence on the free surface. This phenomenon results in unsteadiness of the vertical velocity profile. Moreover, secondary flows in river bends cause velocity variations, accordingly leading to changes in shear stress near the bed. The present study evaluates and analyzes the effect of streamlines variations, maximum velocity distribution, and secondary flow strength on bed shear stress distribution along a 180 degree sharp bend built in the Hydraulic Laboratory of Persian Gulf University. Results suggest of the occurrence of maximum secondary flow strength at the second half of the bend. The evaluation of bed shear stress distribution using the TKE, modified TKE, and Reynolds methods at turbulent boundary layer demonstrated that the maximum shear stress occurred from the entrance of the bend to the bend apex area near the inner wall. Moreover, comparison of the Reynolds shear stress method at distances of 5 and 15% of the flow depth from the bed indicated that the maximum shear stress occurring at the lower layer moved from the 40 degree cross section to 60 degree cross section at the upper layer.
机译：河流自由表面附近的高流速是由于河床附近存在剪切应力，而自由表面上却没有剪切应力。这种现象导致垂直速度分布不稳定。此外，河道中的二次流动会引起速度变化，从而导致河床附近的剪切应力发生变化。本研究评估和分析了流线变化，最大速度分布和二次流强度对沿波斯湾大学水力实验室建造的180度急弯处的床层剪切应力分布的影响。结果表明在弯曲的后半部分出现了最大的二次流动强度。使用TKE，改进的TKE和Reynolds方法在湍流边界层上评估床层切应力分布表明，最大切应力出现在从弯道的入口到内壁附近的弯道顶点区域。此外，雷诺剪切应力法在距床层流深5％和15％的距离处的比较表明，在下层产生的最大剪应力从上层的40度截面移动到上层的60度截面。

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