Abstract：To investigate the characteristics of flow in a pumpturbine in turbine mode at high flow rates, a geometrical model was established based on the prototype model of the pumpturbines for a pumped storage power station. The shear stress transport (SST) k-w turbulence model and the pressurevelocity coupling scheme SIPLEC were used to simulate the internal flow fields in the model by means of two kinds of mesh, i.e. structured and unstructured, and the obtained results were compared with the measured data.It was shown that there were periodically distributed vortexes in flow passages of the runner at a high flow rate. The scale of the vortexes steadily became larger and extended to the blade trailing edges with increasing of flow rate, causing energy losses.Moreover, such vortexes occupied some crosssectional area of the passages, then the fluid velocity near the pressure sides of blade ascended. This vortex dominated flow has a high demand on quality of mesh in simulation, and it is the reason why the flow in high flow rates is difficult to be simulated.These conclusions can provide a theoretical basis for analysis and simulation of flow at a high flow rate.
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