Experimental investigation of propeller blade back cavitation induced pressure pulses by synchronous observation

This paper investigates the impact of the propeller blade back cavitation on the induced pressure pulses. The study employs synchronous observation, wherein both cavitation and pressure pulses are measured concerning both time and space for a 4-bladed propeller in 5 different conditions. The correlation between the cavitation pattern and pressure pulses is presented to elucidate the mechanism behind the formation of the time history curve of pressure pulses. The results reveal that the pressure pulses induced by propeller cavitation exhibit a combination of consistency and discrepancy. It is demonstrated that the pressure pulses are directly proportional to the second derivative of the cavitation volume curve, allowing for the prediction of pressure pulses by the cavitation volume curve. The disturbances and cavitation evolution on each blade, superposition of adjacent blades, and fluctuations in cavitation collectively contribute to a distinctive curve of propeller cavitation-induced pressure pulses, ultimately determining its frequency spectrum. As the cavitation develops, the amplitudes and blade phase angles of 1st and 2nd blade frequency components of pressure pulses gradually increase. The higher-order components generally increase in amplitude, albeit with varying distributions and no regularity in phase angle variations.