左右非対称なデミハルを有する双胴船の性能に関する実験的研究

摘要

船の形態の1つに2つの船体がデッキ部分でつながった双胴船がある。双胴船は，一般的な単胴船に比べ，広い甲板面積を確保できるという特長があり，フェリー等で広く用いられている。双胴船の船体の1つをデミハルと呼ぶ。デミハルは，単胴船と同じく左右対称の船型が使用されることが多い。しかし近年では，燃料費の削減のため，左右非対称なデミハルを採用して船の推進性能の向上を図る試みが行われており，実船にも採用され始めている。%To capture the ship performances of a catamaran with asymmetric demi-hulls, tank tests were carried out such as resistance test in still water, measurement test of wave height of wash, seakeeping test in regular head waves and captive test for measuring hydrodynamic forces on maneuvering using a scaled model with 2.036m in length. To investigate the effect of clearance of the demi-hulls on the performances, the clearance was changed in the tests as W/B = 2.55, 2.90 and 3.25, where W denotes the breadth overall and B the breadth of the demi-hull. Also, two ship models with different load water line tendencies were used: one is the inside flat and outside round type (IF-type) and the other the outside flat and inside round type (OF-type). The test results obtained are as follows: Residual resistance coefficient of W/B = 2.90 in IF-type is the smallest at the design speed corresponding to Froude number F_n = 0.44 and that of W/B = 2.55 in OF-type is secondary small. In the maximum wave height of the wash, OF-type is almost 30% smaller than IF-type in any demi-hull clearances. In both performances of heave and pitch motions, and added resistance in head waves, OF-type is superior to IF-type near the design speed. Smaller demi-hull clearance and IF-type are better in course keeping performance. The course keeping and turning performances are suitable in any conditions of the catamaran.