Modeling and simulation of sloshing motion in partly filled tank

Abstract

With the increasing consume of LNG all over the world, transport of LNG through sea becomes more and more important. When LNG carrier is on wave with partly filled tank, sloshing will occur and cause damage to the structure of tank, or affects vessel's ability. Sloshing load nowadays has become a important design parameters as the fatigue consideration. To study this sloshing phenomenon, this thesis carried out a numerical method to simulated the sloshing in partly filled LNG tank with different kinds of shapes, which are prismatic, rectangular and cylindrical tanks. The software STAR-CCM+ is used to model and simulated the sloshing motion, both two dimensional and three dimensional models are involved. Four kinds of tank motions are considered: surge, sway, roll and pitch motion. The tank is excited by a regular sin or cosine waves with natural frequency. Natural frequency of specific tanks is calculated and confirmed. Different kinds of liquid filling levels 30%, 50% and 70% are included. Moreover, the numerical results of the free surface movements are compared with the published experimental results and a good agreement is obtained. In addition, three dimensional effects is found and discussed. Furthermore, some inner structure--baffle is used to reduce the sloshing motion and compared.