Unlined pressure tunnels in sound rock, combined with pressurized sand traps at the downstream end, allow for low-cost construction of hydropower tunnel systems. This design concept is utilized in hydropower plants across the world. Currently, many such power plants are being upgraded with higher installed capacity, which may result in challenges with the sand trap efficiency. A physical scale model test, accompanied by 3D CFD simulations of a case study pressurized sand trap, has been studied for economic retrofitting. The geometric model scale is 1:36.67 while the velocity scale and sediment scale are 1:1 (same average flow velocity and sediment size in model and prototype). This is currently an uncommon scaling approach but with several advantages, as presented in this paper. Various options for retrofitting were investigated. A combined structure of ramp and ribs was found to significantly improve the sediment trap efficiency. The main novelties from this work are the proposed design of the combined ramp and rib structure. Secondary results include an efficient setup for physical scale models of pressurized sand traps and a methodology that combines the benefits of 3D CFD simulations with physical scale models testing for sand trap engineering and design.

中文翻译：

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水力发电厂承压式隔砂器的改造

坚固岩石中的无衬里压力隧道，结合下游端的加压沙坑，允许低成本建设水电隧道系统。这种设计理念被世界各地的水电站采用。目前，许多此类电厂都在升级装机容量，这可能会导致沙坑效率面临挑战。一个物理比例模型测试，伴随着一个案例研究加压沙坑的 3D CFD 模拟，已经被研究用于经济改造。几何模型比例为1：36.67，而速度比例和泥沙比例为1：1（模型和原型中的平均流速和泥沙尺寸相同）。这是目前一种不常见的缩放方法，但有几个优点，如本文所述。对改造的各种选择进行了研究。发现斜坡和肋的组合结构显着提高了沉积物捕集效率。这项工作的主要新颖之处在于提出了组合坡道和肋结构的设计。次要结果包括加压沙坑物理比例模型的有效设置，以及将 3D CFD 模拟的优势与沙坑工程和设计的物理比例模型测试相结合的方法。