Hydro-Acoustic Analysis of the Cavitating Model Propeller PPTC in Oblique Flow
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Propeller cavitations and propeller induced pressure pulses in oblique flow were calculated on the propeller model of PPTC. Through the partition of tip vortex field and the refinement of the field gridding, the tip vortex cavitation was simulated based on the homogeneous mixture flow model and Zwart-Gerber-Belamri cavitation model and the computed results of the thrust coefficients and pressure pulses agreed well with the EFD data. Then, cavitation noise was calculated based on the Lighthill’s acoustic analogy. Acoustic sources included monopole and dipole and partially quadrupole sources by selecting the rotating propeller blades and hub as integration surface. One of the aims is to reveal the differences between hydrodynamic pressure pulses and sound pressures. It’s shown that the hydrodynamic pressure pulse and the sound pressure are both characterized with blade passage frequency (BPF); the amplitude of sound pressure is smaller than that of pressure pulse; and their phases are approximately in contrast, when pressure pulse is at the peak, the sound pressure is at the valley. The second aim is to investigate the effects of cavitation. It’s shown that cavitation increases sound pressure but not hydrodynamic pressure pulse. As to the comparison among the perturbation amplitudes of three proximity points, it’s shown that it’s the computed SP that agrees well with the experimental PP, but not the computed PP. It may be necessary to separate and analyze distinctly the hydro-acoustic and hydrodynamic components of the recorded proximity pressure signals.