프로펠러 후류와 선미반류에 의해 영향을 받는 방향타의 간극 캐비테이션에 대한 연구

Abstract

The main objective of the present study is to investigate the characteristics of complex flow around a semi-spade rudder using visualization techniques and pressure measurements. To reduce the scale effects as much as possible in the given experimental conditions, 1/28.5-scale-down models of propeller and rudder are employed in this study. Since the propeller slipstream comes with some angle of attack to the upper part of the rudder in the port side, highly accelerated leakage outflows are separated greatly at the discontinuities of the gap and generate strong cavitation at lower pintle on the suction side. The propeller slipstream influences the pressure distribution up to X/C = 0.28 from the leading edge of the horn. On the other hand, the hull wake reduces the cavitation strength a little in the condition of propeller operation. From the result of pressure measurements the angle of attack formed by the propeller slipstream at the leading edge of the rudder horn is estimated 6 degrees to 8 degrees. PIV results show that the flows coming from the gap of the suction side seem to have periodic behaviors in the flow fields and are related to the unsteady cavitation around the lower pintle. In addition, it was found that the movement of the propeller wake sheet is related to the gap leakage and the possible gap cavitation