Racks retain debris in wastewater treatment plants and shield sensitive machinery in numerous engineering applications. In open-channel flows, racks impound the upstream water level by posing local obstacles in the flow. Based on experimental investigations, empirical approaches usually predict the flow resistance by relying on Bernoulli’s energy principle. Since this principle does not correctly consider downstream conditions such as submerged flows, we present a more accurate workflow to determine the flow resistance based on the Saint-Venant equations. We will demonstrate how the loss coefficient and the hydraulic head loss are determined more reliably without adding complexity to the engineering realisation. In contrast to relying solely on two cross-sections with Bernoulli’s energy principle, applying the Saint-Venant equations enables determining the flow depth profile and the flow velocity in the entire channel. This workflow additionally allows predicting the channel’s hydraulic capacity and freeboard in arbitrary applications.

中文翻译：

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使用 Saint-Venant 方程确定机架的流动阻力和通道中产生的流动动力学

在许多工程应用中，机架保留污水处理厂中的碎片并保护敏感机械。在明渠水流中，支架通过在水流中设置局部障碍物来限制上游水位。基于实验研究，经验方法通常依靠伯努利能量原理来预测流动阻力。由于该原理没有正确考虑淹没流等下游条件，因此我们提出了一个更准确的工作流程，以根据 Saint-Venant 方程确定流动阻力。我们将演示如何在不增加工程实现复杂性的情况下更可靠地确定损失系数和水头损失。与仅依靠伯努利能量原理的两个横截面相比，应用圣维南方程可以确定整个通道中的流动深度剖面和流速。此工作流程还允许在任意应用中预测渠道的水力容量和干舷。