An Experimental Study on Mariner-Type Rudder Cavitation

Abstract

This paper presents the results of investigation made by model experiments for the purpose of preventing cavitation erosion that often occurs in Mariner-type rudder of contanier ship, by taking into account the effect of thickness chord ratio of rudder (t/B, where t=rudder thickness, and B=rudder chord) and the effect of twisting angle designed considering the propeller induced velocity direction on the rudder surface static pressure. The ship chosen for this investigation is of a single screw, single rudder ship with L_<pp>×B×d=200m×30m×9.5m; and V=24.7kt. The results obtained are: 1) It was made clear that there is a possibility of occurrence of cavitation-erosion, when the thickness chord ratio (t/B) is on the order of 0.27, and ship speed range is from 24 to 25 kt. 2) It is suggested that an effective countermeasure may be provided to a rudder with such a twisting angle that coincides with a direction of the propeller induced velocity.