Numerical simulation of unsteady cavitating flows of pumpjet propulsor

In this study, an attempt has been made to study the cavitating flows of a pumpjet propulsor. A numerical study based on the unsteady Reynolds-averaged Navier-Stokes computational fluid dynamics method of homogeneous multiphase using structured grids and the shear stress transport (SST) k- turbulence model has been carried out. Considering the effects of non-condensable gas (NCG) on the cavitation performance, the Schnerr-Sauer cavitation model has been applied and improved by introducing the NCG. The numerical calculations of non-cavitating and cavitating flows for the marine propeller E779A are carried out with different advance ratios at several cavitation numbers to verify the numerical simulation method. Results show that the thrust, the torque, and the cavitation performance, such as the cavitation location and shape, are in good agreement with experimental data. Furthermore, numerical predictions for a pumpjet propulsor on an unmanned underwater vehicle are made with different non-cavitating and cavitating flow conditions. The numerical simulations accurately predict the propulsor efficiency changes and the cavitation inception and extension on the suction side of rotor blades. The circumferential distributions of velocity components in different regions along the axial direction have different characteristics. The pressure distributions around rotor and stator blades are reasonable and consistent with the cavitation phenomenon. Additionally, the existence of a tip vortex and tip clearance cavitation leads to a further loss in efficiency of cavitating flows.