Research on thrust fluctuation and flow field characteristics of pump-jet propulsor in XLUUV's hull wake

Serving as the core propulsion system of Extra Large Unmanned Underwater Vehicle (XLUUV), the pump-jet propulsor (PJP) directly affects XLUUV's speed performance, maneuverability and reliability. This study establishes a high-fidelity numerical simulation method for the flow field of PJP under hull wake of XLUUV based on Large Eddy Simulation (LES). The reliability of this method is validated through comparison with open-water experiments. It investigates the thrust fluctuation and flow field characteristics of the PJP under different forward speeds and different oblique flow angles. Results indicate that, under different forward speeds, the thrust variation law of PJP rotor blade is consistent, and the frequency-domain thrust peaks of each component mainly occur at first-order blade passing frequency. When subjected to oblique flow, the thrust of the PJP rotor decreases, that of the duct increases, while the thrust of the stator exhibits no obvious regularity. With the increase in the oblique flow angle, the thrust amplitude in the frequency domain generally shows an increasing trend. Flow field analysis reveals that the transverse component of oblique flow generates backflow and forms separated vortex at the stern of the hull, which severely impairs the velocity uniformity of PJP rotor disk, leading to an increase in thrust amplitude. This study elucidates the influence mechanism of the hull wake on the inflow quality of the PJP under complex operating conditions, providing a theoretical basis for the vibration and noise reduction design of the PJP.