A method to estimate internal fluid pressure in tanks during ballast water exchange at sea

This paper introduces a method to assess the fluid pressure loads in ship's ballast tanks during ballast water exchange at sea. Two-dimensional problem of sloshing in rectangular tanks with time varying water level is investigated by using modal analysis technique, which has been widely used to solve the general structural vibration problems. Since the method is based on a linear theory, computational simulation of fluid motion can be performed efficiently for whole duration of ballast exchange which typically takes a few hours for each tank depending on the size of the tank and the pump capability. A focus of this study is on the possibility of a resonance of the fluid motion within a limited duration when the level of ballast water gradually changes and the natural frequency may pass through the dominant exciting frequency of ship motions in a stochastic seaway.