New types of fish guidance structures with vertical curved bars and a subsequent bypass system represent a promising technical solution for the protection and guidance of downstream moving fish at run-of-river hydropower plants and water intakes. These so-called “curved-bar rack bypass systems” (CBR-BSs) function as a mechanical behavioral barrier and are characterized by low hydraulic losses, a symmetrical downstream flow field and an overall high fish guidance efficiency in the laboratory for a wide array of European freshwater fish species. This paper presents the results of the hydraulic and live-fish laboratory tests of an optimized CBR-BS configuration with a bar spacing of 50 mm and 30° rack angle to the flow direction. The tests were conducted with six different fish species in an ethohydraulic laboratory flume at different approach flows (0.5 m/s, 0.7 m/s) and different bypass entrance velocities (0.6–1.0 m/s). A numerical model was used to simulate the flow fields in the CBR-BS in order to link the fish behavior to the hydrodynamic cues created by the CBR-BS. Lower approach flow velocities decreased the hydraulic cues of the CBR, which led to more rack passages. A 20% velocity increase towards the bypass entrance significantly increased the fish guidance efficiency compared to a 40% velocity increase. The tested CBR-BS resulted in overall higher interspecies fish protection and guidance efficiencies compared to the more commonly applied horizontal-bar rack with a narrow bar spacing of 20 mm. Recommendations for a sustainable and cost-effective application of CBR-BSs are given.

中文翻译：

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在创新的弯杆架旁路系统中下游移动鱼的游泳行为，用于在进水口保护鱼类

带有垂直弯曲杆的新型导鱼结构和后续的旁路系统代表了一种很有前景的技术解决方案，用于在径流式水电站和取水口处保护和引导下游移动的鱼。这些所谓的“弯杆架旁通系统”（CBR-BS）用作机械行为屏障，其特点是水力损失低，下游流场对称，在实验室中对鱼的引导效率高，适用于广泛的阵列欧洲淡水鱼种类。本文介绍了优化的 CBR-BS 配置的液压和活鱼实验室测试结果，该配置具有 50 毫米的钢筋间距和 30° 的机架角度与流动方向。在不同的进水流量（0.5 m/s、0.7 m/s）和不同的旁路入口速度（0.6-1.0 m/s）下，对六种不同的鱼类在一个ethohydraulic实验室水槽中进行了测试。数值模型用于模拟 CBR-BS 中的流场，以便将鱼的行为与 CBR-BS 产生的水动力线索联系起来。较低的进场流速降低了 CBR 的液压信号，从而导致更多的齿条通道。与速度增加 40% 相比，旁路入口处速度增加 20% 显着提高了鱼的引导效率。与更常用的具有 20 毫米窄条间距的水平条架相比，经过测试的 CBR-BS 导致总体上更高的种间鱼类保护和引导效率。