Numerical study on the wake dynamics and vortex system in a pump-jet propulsor
Description
Pump-jet propulsors are widely used in underwater vehicles such as submarines due to their advantages of high efficiency and low noise. In this paper, the wake dynamics of a pre-swirl stator pump-jet propulsor is numerically investigated using the improved delayed detached eddy simulation method and sliding mesh method. The phase-averaged and instantaneous wake fields are analyzed. The evolution mechanisms of tip leakage vortex are revealed with volume rendering technique and spectral analysis. The results show that the wake exhibits a serrated high-speed region, and its stable extension range expands with the increase of the advance ratio. Moreover, the short-wave instability is found to be the primary mechanism of vortex breakdown. Power spectrum analysis shows that there are distinct peak values at the blade passing frequency and its harmonics in the rotor region. Under zero inflow condition, the rapid breakdown of the vortex system makes the energy migrate to a wider frequency band, which may increase the risk of resonance. The study reveals the evolution of the multi-scale vortex structures in the wake field of the pump-jet propulsor and provides important support for the design and optimization of pump-jet propulsor.