Numerical Investigation on Cavitation Vortex Dynamics of a Centrifugal Pump Based on Vorticity Transport Method

Cavitation is one of the most important aspects of the stable and safe operation of a centrifugal pump. To examine the dynamics of cavitation vortex in a centrifugal pump, the cavitating flow is investigated by using the modified shear stress transport (SST) k-& omega; turbulence model with the Zwart cavitation model. The numerical results are confirmed by comparing them with those obtained from experimental tests. The results show that there is a critical cavitation number of & sigma;(c) at each flow rate condition. As the cavitation number & sigma; exceeds & sigma;(c), the pump head remains stable. Conversely, the head rapidly decreases when the & sigma; falls below & sigma;(c). As the & sigma; decreases, the pump experiences successively incipient cavitation, slight cavitation, and severe cavitation. At the stage of severe cavitation conditions, the vortex structures are generated at the tail of cavitation in the flow passage. The vorticity transport method is employed to analyze the vortex dynamics, and it is found that the vortex area contains high vorticity. The dominant contribution to the generation of vorticity comes from the vortex stretching and dilation terms acting in different directions. The contribution of the baroclinic torque to vorticity generation at the vapor-liquid interface is significant. The Coriolis force has a negligible impact on vorticity transport.