Numerical Prediction of the Pumpjet Propulsor Tip Clearance Vortex Cavitation in Uniform Flow

Abstract

Previous studies show that the tip clearance loss limits the improvement of pumpjet propulsor (PJP) performance, and the tip clearance flow field is the most complicated part of PJP flow. In this work, the non-cavitation and cavitation hydrodynamic performances of PJP with a tip clearance size of 1 mm are obtained by using the detached-eddy simulation (DES). At constant oncoming velocity, cavitation first occurs on the duct and then disappears with the decrease of the advance ratio. The rotor blade cavitation occurs at the low advance ratio and comprises tip clearance cavitation, tip leakage cavitation, and blade sheet cavitation. In the rotor region, the typical vortices include tip separation vortex, tip leakage vortex, trailing edge shedding vortex, and blade root horseshoe vortex. Combined with the pressure distribution, both the Q and λ2 criteria give reliable results of vortex identification. The cavitation causes an expansion of tip leakage vortex in the circumferential direction and decreases the intensities of tip separation vortex in the whole tip clearance area and tip leakage vortex in the cavitation area, and enhances the strength of tip leakage vortex in the downstream non-cavitation area.