旋转叶栅空化流动的涡动力学特性OA

In order to investigate the vortex dynamics characteristics in rotating cascades during cavita-tion,numerical simulations were performed using the detached eddy simulation(DES)model combined with the Zwart-Gerber-Belamari cavitation model,and experiments were carried out to verify the reliability of the numerical calculation method.Furthermore,the distribution laws of cavitation bubbles,streamlines,vortex structures,vorticity,vorticity transport terms,and turbulent kinetic energy in the impeller were analyzed.The results show that as the cavitation number decreases,high-velocity fluid is formed in the flow passage and disturbs the cavitation bubble interface.Cavitation bubbles and vortices are coupled with each other and block the flow passage,leading to a decline in the hydraulic performance of the rotating cascade.Furthermore,the growth of cavitation bubble volume promotes vortex generation,while the intense gas-liquid exchange at the vortex and cavitation bubble interfaces is a key factor affecting vorticity changes.The contribution of the Coriolis force term to vorti-city is relatively small,however,at low cavitation number,the contribution of the Coriolis force term to vorticity in the vortex structure region at the tail of cavitation bubbles increases significantly.As the cavitation number decreases,the region of high turbulent kinetic energy variation region and the turbu-lent kinetic energy loss per unit mass of fluid in the impeller gradually shift from the blade leading edge to the blade trailing edge.The main causes of turbulent kinetic energy loss include the collision between fluid and blades,cavitation development,and the vortex motion at the tail of cavitation bub-bles during the unsteady cavitation stage.The research results can provide certain theoretical support for reducing the cavitation flow instability of hydraulic machinery.