尾水管涡带非定常流动数值模拟

Numerical Investigation of Unsteady Flow Fields in a Elbow Draft Tube

基于雷诺时均N-S方程和标准k-ε双方程湍流模型,对混流式水轮机尾水管内部的三维定常湍流进行了计算。对加和不加出口尾水箱分别进行了定常计算,比较了两者的收敛性,肯定了尾水箱的作用;同时给定尾水管周期性旋进进口边界条件,对尾水管进行了非定常流动计算,分析了尾水管压力脉动和水流运动情况,认为尾水管流场及涡动现象基本和实际符合,结果表明了给定的进口速度模型的逼近真实性。

Based on Reynolds equations closed by k-ε turbulence model with general coordinates, the numerical simulation of three-dimensional turbulent flow in an elbow draft tube was conducted. And the inlet boundary conditions of draft tube are presented on the basis of former research findings and experimental data. The steady flow with or without outlet tank was calculated respectively. The convergence procedure of the two conditions was compared and the results show that the outlet extended tank has a positive effect. Secondly, by given the inlet boundary condition of the draft tube as periodical rotational flow, numerical unsteady flow was calculated and the flow field structures, the characteristics of swirling flow and the pressure fluctuation in the draft tube were gained. The calculation results indicated that by using dynamic inlet boundary condition the numerical simulation results were much more rational and similar to practical experiment results, which assure that the inlet velocity model is very close to the authenticity.