プロペラのスキューが不均一流中キャビテーション性能に及ぼす影響について

抄録

Six propellers with different skew angle distributions and constant pitch distributions are selected in order to clarify the skew effects on unsteady cavitation characteristics of marine propeller in non-uniform flow fields. Using these propellers, the effects of the skew angle and the skew distributions on characteristics of propeller cavitation were investigated experimentally. Cavitation observations, hull pressure measurements above the propeller, cavity thickness measurements, paint tests and noise measurements were carried out in two different wake fields. One is a model wake distribution of a car carrier which had been adopted in comparative erosion tests of 17th ITTC, the other is the estimated ship wake distribution by Sasajima and Tanaka's method. The results of the experiments show the reduction of the hull pressure amplitude as the increase of skew angle, while the cavity volume increases in proportion to the increase of skew angle. The effect of increase in skew angle seems to reduce the extent and weaken the impulsive pressure of the cloud cavitation which occures when unsteady cavity collapses. This is supported by the results of paint tests and cavitation noise measurements. The falling off area of the paint on suction side of propeller blades and the sound pressure level are reduced as the increse of skew angle.