ABSTRACT
It is well known that partial loading in the membrane LNG tanks may lead to a violent sloshing phenomenon and it can cause structural damages to the tanks. In this study, in order to understand the basic characters of sloshing, we carried out model experiments and measured the liquid global forces, sloshing pressures and liquid motion in the model tanks. In the model experiments, a liquid rotating motion in the tank (swirling) was observed in some test cases. Swirling phenomenon has not been discussed in detail in membrane tanks, however, in some cases we observed that the liquid motion became very violent. We, therefore, studied membrane tanks with different tank-length-to-tank-breadth ratio and examined the conditions of the occurrence of swirling. We also examined the sloshing loads in irregular waves and investigated the relationship between sloshing loads and ship’s motion response spectra. A practical formula that predicts the sloshing load was obtained. The results obtained from this study are considered to be useful for not only the designers but also for the operators of LNG carriers.
