Turbulent flows are investigated upstream of a bar rack system that is recommended as optimum in recent literature from tests with several fish species of different morphology, swimming ability, and behavior. Both two-dimensional two-component and two-dimensional three-component state-of-the-art particle image velocimetry were used to quantify and analyze hydrodynamic metrics important for downstream migrating species. The inclination angles of the bar and rack were 45° and 30°, respectively, and the thickness of the bottom overlay was 13% of the water depth. The two Reynolds numbers investigated, based on incoming velocity and bar thickness, were 4,000 and 6,000. The statistical and structural characteristics of turbulent flows in the streamwise-spanwise plane at 5% water depth, and the streamwise-vertical plane at channel mid-span are discussed. Upstream of the bottom overlay, the mean flow is deflected and accelerated toward the bypass, leading to an increase in the Reynolds stresses, while the turbulence eddies become smaller. For effective fish guidance, it is recommended that sweeping velocity (V_p) be larger than normal velocity (V_n), with V_p parallel and V_n perpendicular to the bar rack and bottom overlay. In the downstream half of the bar rack, V_n may increase sufficiently to surpass V_p near the bypass, possibly reducing effective guidance for some species and sizes. Upstream of the bars, the levels of streamwise mean velocity vary abruptly, which may deter fish from contacting the bars. Although inferences on passage effectiveness are made based on previous studies, tests with different species and sizes are needed to confirm fish responses.

中文翻译：

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全面的流动湍流指标可改善下游洄游鱼类的杆架引导


在最近的文献中，通过对几种不同形态、游泳能力和行为的鱼类进行测试，推荐该系统为最佳系统，对湍流进行了研究。二维二分量和二维三分量最先进的粒子图像测速技术都用于量化和分析对下游迁移物种重要的水动力指标。杆和架的倾斜角度分别为45°和30°，底部覆盖层的厚度为水深的13%。根据传入速度和棒材厚度调查的两个雷诺数分别为 4,000 和 6,000。讨论了5%水深处的流向-跨向平面和河道跨中的流向-垂直面湍流的统计和结构特征。在底部覆盖层的上游，平均流向旁路偏转并加速，导致雷诺应力增加，而湍流涡流变得更小。为了有效引导鱼，建议扫掠_速度（ Vp ）大于正常_速度（ Vn ），其中Vp平行于杆架和底部覆盖层，Vn_垂直于杆架和底部覆盖层。在杆架的下游一半， V _n可能会增加到足以超过旁路附近的V _p ，这可能会减少对某些物种和尺寸的有效引导。在坝的上游，流向平均速度水平突然变化，这可能会阻止鱼类接触坝。 尽管对传代有效性的推论是根据以前的研究得出的，但需要对不同物种和大小进行测试来确认鱼类的反应。