压力进水口的最小淹没水深

水电站、水泵站以及其它压力引水隧洞的进水口都要求有一定的淹没深度，以避免出现挟气漩涡引起有害的工程问题．其计算公式分为三种类型：以进口高度表示的公式、以进口流速水头表示的公式以及以弗汝德数Fr表示的公式；根据三峡电站模型实验的数据比较了各公式的计算值，结果发现，以戈登公式的计算结果最为接近实验值，但在工程实践中证明，大流量、高流速的情况下，戈登公式并不能给出足够的安全淹没深度，其主要原因在于边界的影响．对于重要的工程，应通过实验确定临界淹没水深．

The Critical Submergence at Pressure Intakes

The paper is concerned with the critical submergence depth below the water surface at pressure intakes, mainly power tunnel intakes. Such a depth could avert air-entraining vortices, which could cause unfa-vorable impact on the performance of hydraulic machines and dangerous hydropneumatic effects in the close conduit system. Three kinds of empirical formulae in term of gate height, or velocity head, or Froude number,were summarized and evaluated. According to the design data of the Three Gorges project, the calculation re-sults from different formulae were compared- lt was found that the prediction from Gordon's formula was al-most same as the result of physical model test. Nevertheless the minimum depth from Gordon is not enough to avoid air-entraining vortices if the inflow discharge is very large and at the same time the average velocity is higher.