Minimum Submergence before Double-Entrance Pressure Intakes

This paper describes a large-scale physical model study concerning the minimum submergence required for double-entrance pressure intakes, such as used for power tunnel intakes. Use of minimum submergence can avert the occurrence of subatmospheric pressure and air-entraining vortices, and avoid reducing the efficiency of the turbine and its vibration of the turbine, etc. The scale of the double-entrance intake model, 1:30, which is primarily designed for the Three Gorges project, is almost the largest in the world. Based on analysis of the experimental data, an empirical formula is obtained and then it is compared with Gordon's formula, which is used mainly to calculate the minimum submergence before single-entrance intakes. The empirical formula is useful in the design of double-entrance pressure intakes.