Experimental Studies on the Maneuverability of a Ship with Stern Bulb

Abstract

This report deals with the maneuverability of a ship with stern bulb (SB), comparing with the conventional inverted G type stern (IG). From the results of model free running tests and full scale sea trials conducted for two 60,000 DWT tankers which have almost the same principal particulars except stern shape. i.e. SB and IG, the maneuvering characteristics of SB is compared with one of IG. Circular motion tests for two ships are also conducted in order to investigate the cause which makes maneuverability of two ships different, by analyzing the hydrodynamic derivatives obtained from tests. As a result, the following conclusions are obtaind. (1) The course stability of SB is less than that of IG on fully loaded condition. (2) The difference of hydrodynamic derivatives of naked hull between two ships causes the less course stability of SB (3) The intensity of bilge vortex in straight running seems to play an important role on characteristics of hydrodynamic derivatives. (4) Judging from comparison of two tankers, the difference of frame line of two aft bodies is more important on course stability than that of stern profile.