A relevant way to promote the sustainable development of energy is to use hydropower.Related systems heavily rely on the use of turbines,which require careful analysis and optimization.In the present study a mixed experimental-numerical approach is implemented to investigate the related mixed water flow.In particular,particle image velocimetry(PIV)is initially used to verify the effectiveness of the numerical model.Then numerical results are produced for various conditions.It is shown that an increase in the guide vane opening can reduce the extension of the region where the fluid velocity is 0 at the inlet of the runner blade,i.e.,it can counteract the generation of the channel vortex;an increase in the guide vane opening also contributes to mitigate the pressure acting on the runner blade;no matter what the working conditions are,the surface pressure is usually higher than that on the suction surface,and there is a cliff-like drop of pressure at the tail of the blade,which indicates that the runner blade tail is more prone to develop backflow.
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