Pooled step cascade weirs are hydraulic structures that are preferred over ordinary weirs due to their application on steep slopes and to their effectiveness in obtaining water aeration. However, these structures are subject to failure due to scour being initiated downstream, or to breakdown due to the high energy of impinging water. In this paper, an experiment was presented to study the effect of the number and ratio of holes in weirs to improve energy dissipation. To improve energy dissipation, cascade weirs with different configurations of openings were proposed. Furthermore, a sluice gate at the upstream of a cascade weir was proposed as a new technique to increase energy dissipation and reduce scour at downstream. Ten models of pooled step cascade weirs (nine models with different hole configurations and one with a sluice gate upstream), in addition to the ordinary weir, were constructed to investigate the effect of the sluice gate and holes on energy dissipation; the range of each type of flow (nappe, transition, and skimming); the relevant Froude number; and the ratio of water depth to critical depth over pooled step cascade weirs. To implement this, the ratio of holes to the area of the weir were between 0 and 21.22% and the number of holes used were one hole, two holes, and three holes. The results concluded that the best method to obtain maximum energy dissipation was putting a sluice gate at the upstream of a solid pooled step cascade up to a discharge of 2.0 l/s. The most effective ratio of holes to weir area was 7.15% at the minimum Froude number when the discharge exceeded 2.0 l/s. Moreover, the ratio of upstream water depth to critical depth decreased with increasing discharge. The nappe, transition, and skimming flow types were increased more on a pooled stepped cascade weir of 7 mm opening diameter with three holes (ratio of 7.15%) than the other models. The Froude number decreased as the hole numbers increased at high discharges for the pooled stepped cascade weir, especially with the hole diameter of 12 mm. Some empirical equations were established to represent the relation between the upstream head and discharge for each case.

中文翻译：

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上游闸门和阶梯级联堰上的孔对能量耗散的影响

池梯级梯级堰是一种水工结构，优于普通堰，因为它们适用于陡坡并能有效地获得水曝气。然而，这些结构会因下游的冲刷而损坏，或因冲击水的高能量而损坏。在本文中，提出了一个实验来研究堰孔的数量和比例对改善能量耗散的影响。为了改善能量耗散，提出了具有不同开口配置的级联堰。此外，还提出了在级联堰上游的闸门作为增加能量耗散和减少下游冲刷的新技术。十种池式梯级堰模型（九种具有不同孔配置的模型，一种具有上游闸门的模型），除了普通的堰外，还建造了用于研究闸门和孔对能量耗散的影响；每种类型的流动（绒毛、过渡和撇脂）的范围；相关的弗劳德数；水深与阶梯级联堰上临界水深的比值。为实现这一点，孔与堰面积的比率在 0 到 21.22% 之间，使用的孔数为一孔、两孔和三孔。结果得出的结论是，获得最大能量耗散的最佳方法是在固体汇集阶梯级联的上游放置一个闸门，流量可达 2.0 l/s。当流量超过 2.0 l/s 时，在最小弗劳德数下，孔与堰面积的最有效比为 7.15%。而且，上游水深与临界水深之比随着流量的增加而减小。与其他模型相比，在开口直径为 7 mm 的三孔汇集阶梯式梯级堰上，推覆流、过渡流和撇渣流类型增加更多（比例为 7.15%）。Froude 数随着池形梯级堰高流量下孔数的增加而降低，尤其是在孔直径为 12 mm 的情况下。建立了一些经验方程来表示每种情况下上游水头和流量之间的关系。尤其是孔径为 12 mm 的情况下。建立了一些经验方程来表示每种情况下上游水头和流量之间的关系。尤其是孔径为 12 mm 的情况下。建立了一些经验方程来表示每种情况下上游水头和流量之间的关系。