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 sigma n and oblique angles theta. The results show that when the sigma(n) 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 K(T )decreases by 28.5%. The influence of sigma(n) on the excitation force is less than that of the theta. When theta equals 0 deg, its excitation force is approximately 1.5 times that when theta is 6 deg. As theta increases from 6 deg to 24 deg, the excitation force increases rapidly, and the excitation force of K(T )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 theta 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 theta is 6 deg. This research provides a theoretical basis for the anticavitation and low-noise design of the PJPs.