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ON THE MOTION OF A SHIP IN RECTANGULAR HARBOR
최항순,In H. Cho 한국해안해양공학회 1989 학술강연회 발표논문초록집 Vol.1 No.1
Herein the surge-heave-pitch motion of a ship in a harbor has been studied within the framework of linear potential theory. Harbors are excited by long waves and moored ships undergo motions, which in turn excites the harbors. In unfavourable situations, collisions with neighboring ships or pier fenders likely occur and result in severe damages. Despite the practical importance, ship motions in harbor have been seldom investigated. As a step to this direction, we approach the problem theoretically. Our primary concern in this paper is to clarify the physics underlined rather than immediate applications. Under this aspect, we have simplified the problem so as to retain the solution manageable. The ship is assumed to be slender, weakly moored along the centerline of a rectangular harbor with constant depth and straight coastline. The wave field in the harbor generated by normally incident waves can be described in terms of Green's function, which is the solution of the Helmholtz equation satisfying all the appropriate boundary conditions. By means of matched asymptotic expansions, the flux condition is imposed at the harbor entrance. The presence and motion of a ship is represented by singularity distributions along its centerline. By invoking the slender body approximation, the source strengths are determined in relation with the ship's geometry. The equation of coupled ship motions is straightforward to solve, once hydroddynamic forces are available. Numerical results are given for ship's responses, tensions developed in the mooring cable and wave fields in the harbor with different aspect ratios.