Abstract The cavitating flow in a mixedflow pump under the design working condition was simulated numerically with the SST turbulence model and homogeneous mixture cavitation model based on the Rayleigh-Plesset equations by solving the timeaveraged Navier-Stokes equations. The NPSHH curve was extracted from the results, the cavitation inception and development were captured as well. The features of vapour volume fraction distribution in the impeller were comparatively analyzed under the slight, critical and severe cavitation conditions. The results show that this pump has met the requirement on its cavitation performance. A cavity appears firstly on the blade suction surface near the leading edge and the shroud， as NPSH is reduced, it extends towards the hub and trailing edge.The tip cavity originates from the blade leading edge and develops into a strip along a blade contour on the shroud. The hub cavity accumulates near the blade trailing edge on the hub, further the vapour volume fraction on the hub is evidently larger than on the shroud. A similar cavity distribution is indentified in all the impeller passages, and the serious blockage due to cavity in the flow passages results in a sharp reduction in pump head under the sever cavitation condition.
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