Estimation of Unsteady Cavitation on Propeller Blades as a Base for Predicting Propeller-Induced Pressure Fluctuations

概要

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In order to calculate the pressure fluctuations induced by a cavitating propeller, the cavity geometry on the propeller blades must be known as a function of time. Purely theoretical calculation thereof needs application of unsteady lifting surface theory including effect of unsteady cavitation, which is, however, far beyond the analytical formulation . In this study, attempts were made to estimate the unsteady cavitation using available theoretical methods (an unsteady theory on non-cavitation, propellers and an approximate method of lift equivalence for determination of cavity length). As a result, the unsteady cavitation on the blades was found to be estimated by lift equivalence method with some empirical factors obtained by the observation of cavity extent and the measurement of cavity thickness. The pressure fluctuation calculated by thus obtained cavity geometry turned out to be about four times as large as the measured values. Multiplying factor 1/4 with calculated pressure due to unsteady cavity, the correlation between the calculated and the measured total pressure fluctuations was found to be fairly good.
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