Numerical investigation on vortex control effect of pump-jet propulsion via porous blade tips

Pump-Jet Propulsions (PJPs) are widely equipped on submarines, torpedoes and other underwater vehicles. The special structure of PJP leads to complex vortex system in the working process, especially the strong Tip Leakage Vortex (TLV) in the clearance between the duct and the rotor blade tips, which seriously affects the unsteady hydrodynamic performance and acoustic characteristics of PJP. The rotor blade tips of PJP are modified with porous materials, the control effect of the porous blade tip on the TLV is investigated, and the influence of the porous blade tips with different parameters on the vortex control effect is quantitatively analyzed. Large Eddy Simulation (LES) method is applied to the flow field observation. It is concluded that the porous blade tips can weaken the TLV intensity and inhibit the backflow at the blade tip clearance. The analysis results of fluctuating pressure indicate that the negative pressure peak and pressure gradient in tip clearance can be effectively reduced after installing porous blade tips, which is helpful to the vibration and noise reduction of the PJP. Through a series of optimization work, the porous blade tip scheme with minimal propulsion performance loss and obvious vortex control effect is determined.