Numerical and experimental investigation of cavitation flows in a multistage centrifugal pump

Cavitation behavior is very important in pumps for long time operation. However, there is difficulty in predicting the cavitation phenomena of pumps by Computational fluid dynamics (CFD). In order to accurately ascertain cavitation behavior, a comparison between CFD and experimental data is a significant and essential process. The purpose of this study is to analyze cavitating behavior in multistage centrifugal pumps numerically and experimentally. For this investigation an experimental set up was used to obtain cavitation performance results. The CFD method was used to investigate the multistage centrifugal pump performance under developed cavitating conditions. The Reynolds-averaged Navier-Stokes (RANS) equations were discretized by the finite volume method. The two-equation SST turbulence model was adopted to account for turbulent flows. Numerical data were validated with experimental data and a good comparison of results was achieved. Numerically, cavitation performances were obtained for different pump stages and the effects on cavitation were described according to different NPSH (Net positive suction head). The occurrence of cavitation was also described according to NPSH3% in the head drop lines and water vapor volume fraction on the impeller blade. The rapid drop in head at low NPSH was captured for different flow conditions. It was found that for stage to stage performance, the head drop changes could be related to losses inside the pump. It was also shown that the simulation results can truly represent the development of the attached sheet cavitation in the impeller.