Cavitation evolution and radiation noise of a pre-swirl pump-jet propulsor in oblique flow

During the submarine's surfacing process, the rotor of the pump-jet propulsor (PJP) is subjected to nonuniform hydrodynamic loads and cavitation, inducing cavitation-induced noise. In this paper, the hybrid Reynolds Averaged Navier–Stokes/Large Eddy Simulation method, the Schnerr–Sauer model and Ffowcs Williams–Hawkings equations are adopted to explore the hydrodynamics, excitation force, radiation noise, cavitation evolution of the PJP with different cavitation numbers σn and oblique angles θ. The results show that when the σn decreases from 1.5 to 1.0, the rapid development of cavitation causes the hydrodynamic performance of the PJP to deteriorate rapidly, and the total thrust coefficient KT decreases by 28.5%. The influence of σn on the excitation force is less than that of the θ. When θ equals 0 deg, its excitation force is approximately 1.5 times that when θ is 6 deg. As θ increases from 6 deg to 24 deg, the excitation force increases rapidly, and the excitation force of KT increases by 4 times. The contribution of the excitation force to noise is reflected below 300 Hz, while the noise in the range of 300–5000 Hz is caused by cavitation. When θ is equal to 0 deg, the spatial distribution of cavitation is relatively uniform, the cavitation volume change rate is the fastest, and the collapse frequencies are almost the same. The cavitation-induced noises are superimposed on each other, and its total sound pressure level is nearly 7 dB higher than that when θ is 6 deg. This research provides a theoretical basis for the anticavitation and low-noise design of the PJPs.