Numerical investigation on hydrodynamic performance of a pre-swirl stator pump-jet propulsor with special emphasis on energy loss mechanism

The objective of this paper is to evaluate the hydrodynamic performance of the newly developed pre-swirl stator pump-jet propulsor (PJP) and to investigate its underlying flow characteristics and energy loss mechanisms. Numerical simulations are carried out for the scaling model of the PJP, the experimental tests are also performed to verify the numerical simulation results. The energy balance equation is loaded to investigate the energy loss combining with vortex structures. The numerical results show a reasonable agreement with the available experiments. The stator performs well for generating pre-swirl flow with tangential velocity, which could be effectively absorbed by the rotating rotor to varying levels under different operating conditions. The stator-rotor interaction flow is complicated and causes obvious non-uniformity for the flow field due to the generation of trailing vortices. The energy losses within the PJP are well quantified and visualized by different loss terms in energy balance equation. The production of turbulent kinetic energy and then dissipates due to viscous effects is the leading cause for energy loss, which originates from vortex evolutions and impact loss without considering the friction loss. The generation of tip leakage vortex dominates the energy loss in the rotor domain and wake field of PJP.