Experimental Study of Sloshing Load on LNG Tanks for Unrestricted Filling Operation

摘要

This paper presents a numerical and experimental study of sloshingloads on liquefied natural gas (LNG) vessels. Conventional LNGcarriers with membrane-type cargo systems have filling restrictionsfrom 10% to 70% of tank height. The main reason for such restrictionsis high sloshing loads around these filling depths. However,intermediate filling depths cannot be avoided for most LNG vesselsexcept the LNG carrier. This study attempted to design a membranetypeLNG tank with a modified lower-chamfer shape that allows allfilling operations. First, numerical sloshing analysis was carried out tofind an efficient height of the lower-chamfer that can reduce sloshingpressure at partially filled conditions. The numerical sloshing analysisprogram SHI-SLOSH was used for numerical simulation; this programis based on SOLA-VOF. The effectiveness of the newly designed tankswas validated by 1:50-scale three-dimensional tank tests. A total of twodifferent tanks were tested: a conventional tank and modified tank. Astest conditions, various filling depths and wave periods wereconsidered, and the same test conditions were applied to the two tanks.During the tests, slosh-induced dynamic pressures were measuredaround the corners of the tank wall. The measured pressure data werepost-processed and the pressures of the two different tanks werestatistically compared in several ways. Experimental results show thatthe modified tank was quite effective in reducing sloshing loads at lowfilling conditions. This study demonstrated the possibility of all fillingoperations for LNG cargo containment systems.