基于重叠网格的水轮机导叶尾流水动力特性数值研究

为研究水轮机导叶运动对水轮机暂态过程中叶栅流场的流固耦合动态特性影响,基于二维时均瞬态N-S方程和标准k-ε湍流模型,分别应用ANSYS FLUENT软件中的重叠网格方法和动网格方法,对高雷诺数下槽道内水轮机单个导叶在均匀来流条件下模拟水流绕流翼型叶片的导叶匀速关闭运动过程.结果表明:2种方法得到的关闭过程中叶后不均匀流场动态水力特性呈现出强非线性,导叶的升力系数、阻力系数随时间的变化规律较为吻合,槽道内各典型时刻的流场压力、尾涡结构、湍流强度分布特征也基本一致.但重叠网格方法的网格数量约为动网格方法的1/3,计算耗时约为动网格方法的1/4,说明重叠网格方法在计算效率方面具有比动网格方法更好的优越性.研究表明2种方法都可较好地模拟导叶动态绕流问题,但对某些复杂非线性动边界流固耦合问题进行非定常流模拟时可以优先选择重叠网格方法,2种方法都具有较高工程应用价值.

Numerical study on dynamic characteristics of flow around a vanes in the channel based on overset meshes

Numerical simulation of turbulent flow around a vane in the channel with guide vane closure based on the two-dimensional transient N-S equation was conducted with the standard k-ε turbulence model. In order to study the dynamic effect of the cascade flow field on the fluid-structure interaction occurring between the flow and guide vanes in the transient process of hydro-turbine, the overset meshes and dynamic mesh technology were used in such an unsteady flow problem. The dynamic characteristics of non-uniform flow field show strong nonlinearity under the two methods. The lift and drag coefficients of a guide vane are in good agreement with time. The pressure, vortex structure and turbulence intensity distribution in the channel at the typical time are basically the same. But the mesh number of the overset mesh is about 1/3 of the dynamic mesh, and the computation time is about 1/4 of the dynamic mesh. It is shown that the overset mesh method has better advantages than the dynamic mesh method in terms of computational efficiency. The results show that the two methods can well simulate the dynamic flow around a guide vane. But for some complicated nonlinear dynamic boundary fluid-structure interaction problems, the overset mesh method is preferred. The two methods are of higher engineering application value.