明满混合瞬变流动仿真计算分析

Simulation of transient mixed free surface pressure flow

在水电站的仿真计算中 ,建立合理可行的明满混合流动数值模型是必要的。针对现有明满混合流动的数值解法中存在稳定性差的缺点 ,提出了一种新的计算格式——特征隐式格式法。其主要思路是将动量和连续方程转化为双曲型方程组的标准形式进行差分。该方法用于三峡、百色等大型电站的仿真计算中 ,计算结果合理可信。文中还研究了洞型对流动特性的影响 。

In the tailrace tunnels of some hydropower stations, transient mixed free surface pressure flow may occur. A computer model is needed to detect and simulate such mixed flows. This paper compares several methods for computing the mixed flow. A new method (Characteristic Implicit Method) with good stability is developed based on the implicit finite difference scheme. The method solves the normal forms of the hyperbolic system made up of the continuity and momentum equations. The new method does not have the stability problems of other methods. Transient simulation programs have been developed using the new method to simulate transient operating conditions in the Three Gorges Hydropower Station and Baise Hydropower Station. The calculated results are reasonable and are used to develop optimum design principle for the tunnel shape.