基于重叠网格的水轮机导流罩水动力特性

为了研究复杂海流环境条件下导流罩对水轮机非定常水动力特性的影响,提出了一种采用基于重叠网格的DFBI(动态流体固态相互作用)数值仿真方法,利用重叠网格解除物体与网格之间的拓扑结构约束.六自由度运动模型DFBI模拟刚体在流体作用下的被动运动,实现了对水轮机在动态来流作用下被动旋转的非定常水动力特性仿真模拟,针对不同来流条件下导流罩对水轮机水动力特性影响进行了对比分析.研究结果表明:采用基于重叠网格的DFBI数值仿真方法,可以精确地监测水轮机由于周围流场变化导致的加速和自适应转动等过程,实现对水轮机非定常水动力特性研究;在设计流速范围内,加装导流罩可以将水轮机周围流场的流速提高约1.35倍,水轮机的转速提高1.2倍,获能效率提高约35%;加装导流罩有助于提高水轮机的平均转速,将水轮机平均获能效率提高约30%.

Hydrodynamic performance of marine current turbine with diffuser based on overlap grid method

A numerical simulation method based on overlap grid, i.e. dynamic fluid body interaction(DFBI), was applied to study effects of diffuser on hydrodynamic performance of a marine current turbine in complex current environments in this paper. Since the overlap grid can remove topological constraints between objects and meshes, DFBI can simulate passive motion of a rigid body under action of fluid to realize the simulation of unsteady performance of a passively rotating current turbine. Particularly, the influences of diffuser on the hydrodynamic performance and the surrounding flow field around the turbine were analyzed under different flow conditions comparatively. The result shows that the met-hod used in the paper can accurately monitor the processes such as speed acceleration and rotor adaptive rotation and so on caused from the changes in current flow field around the turbine, and consequently investigating into unsteady performance of the turbine becomes realizable. An installed diffuser can increase the current velocity around the turbine by around 1.2 times, raise the turbine speed by 1.2-fold and improve the turbine power coefficient by about 35%. Under unsteady current flow conditions, the averaged power coefficient is reduced by about 33%. The diffuser can increase the turbine average rotational speed, but also can raise the average power coefficient by approximate 30%.