Due to the high flow velocity and easy cavitation of high-head drainage tunnels, it is usually necessary to set up aeration facilities. In particular, when the bottom slope of the tunnel is mild, the aeration facilities often have problems such as difficulty with air intake, short cavity, and serious water accumulation, which aggravate the risk of cavitation damage. In this paper, based on the Rumei hydropower station and the Gushui hydropower station, a method combining theoretical analysis and model testing is used to solve the connection problem between the aeration facility and the 3% mild bottom slope of a tunnel body, and the aeration facility shape of “lifting ridge + flat (mild) slope + steep slope” is put forward. The research shows that the steep slope section can smoothly connect the water flow over the cantilever, reduce the jet impact angle, prevent the water from backtracking, and produce a long and stable cavity in the flat (mild) slope section. The aeration concentration along the bottom of the tunnel is higher than 3% at 140 m over the top of the dam. The aeration effect of this type is better, and it can provide effective long-distance protection for a drainage tunnel with high head and a mild bottom slope.

中文翻译：

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缓底坡高水头泄放隧道曝气器形状研究

由于高水头排水隧道流速高，容易产生气穴，通常需要设置曝气设施。尤其是隧道底坡较缓时，曝气设施往往存在进气困难、空腔短、积水严重等问题，加剧了空泡破坏的风险。本文以如梅水电站和固水水电站为基础,采用理论分析与模型试验相结合的方法,解决了曝气设施与隧道体3%轻度底坡的连接问题,以及提出“提升脊+平（缓）坡+陡坡”的设施形态。研究表明，陡坡段可以顺利连接悬臂上方的水流，减小射流冲击角，防止水回溯，在平（缓）坡段产生长而稳定的空腔。在坝顶上方140 m处，隧道底部的曝气浓度高于3%。这种类型的曝气效果较好，可为高水头、底坡较缓的排水隧道提供有效的远距离保护。