ABSTRACT

The moonpool is a vertical opening through the deck and hull of a ship used for marine and offshore operations. The water surface motion in the moonpool has resonant behavior with respect to different possible free water surface modes, such as the piston mode, where the water inside the moonpool behaves up and down, and the sloshing mode, back and forth in-between the vertical walls. This paper presents combined theoretical and experimental studies on the moonpool water surface response of a ship in wave conditions. The problem is treated in three dimensional linearized potential theory and is introduced an artificial damping inside moonpool wall. Conducting the model tests in some wave conditions, the R.A.O.s of water surface response of moonpool are compared with numerical results and show generally good agreements. The influence of the artificial damping inside moonpool wall can be qualitatively and quantitatively described the moonpool water surface response. To apply the numerical estimation procedure, we demonstrate the effect of appendage on moonpool wall to prevent the over-flow of the water surface.

INTRODUCTION

The moonpool is a vertical opening through the deck and hull of ship used for marine and offshore operations. The water surface motion of the moonpool has resonant behavior with respect to different possible free water surface mode, such as, the piston mode, where the water inside the moonpool behaves up and down, the sloshing mode, back and forth in-between the vertical walls. Molin [2001] treated the problem in two and three dimensions, via linearized potential flow theory. The natural modes of oscillation of the inner free surfaces are determined, under the assumption of infinite water depth and infinite length and beam of the ships that contain the moonpools. So the ship is assumed to be motionless.

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