构皮滩水电站泄洪中孔出口布置型式分平底式和上弯式两类，其最大运行水头 95.36 m ，事故检修门采用倾向上游的斜门槽，门槽区域流速超过30m/s。由减压模型试验成果知，上弯式中孔门槽区蒸汽型空化强度未超过初生阶段，其体型基本上为免空蚀体型；平底式泄洪中孔门槽区域空化严重，蒸汽型空化达发展阶段，通过体型优化方案比较，采取减小有压段出口面积或扩大有压段断面尺寸的措施都可有效解决上述问题。因此泄洪建筑物有压段内布置斜门槽时，应控制门槽断面平均流速不宜过大，否则其会较直门槽更易产生危害性较大的空化。

In Goupitan Hydropower Station, the layout type of middle discharging orifice was classified into flatbottomed type and upbended type, the maximum operational water head was 95.36 m, and the emergency maintenance gate used an upstream slanted slot，the velocity in the slot region was over 30 m/s. From the result of vacuum tank experiment, the cavitation intensity steam type in the slot region of the upbended type middle orifice did not surpass initial stage. The structural configuration of this middle orifice basically belongs to cavitation free type. The cavitation intensity in the slot zone of the flatbottomed type middle orifice was severe. The steam type cavitation reached developing stage. According to the comparison of structure optimal schemes, adopting a measure of reducing the area of pressure section outlet or enlarging the dimension of pressure section could solve the above problem effectively. Therefore, when a slanted slot was laid in pressure section of discharging structure, the mean velocity of slot section should be controlled below a feasible value, otherwise, the rather serious cavitation would happen more easily in the slanted slot, compared to the straight slot.