Experimental and Numerical Study of an Anti-Sloshing Floating Device for Membrane-Type LNG Tanks

Recent developments with offshore terminals and floating liquefied natural gas (FLNG) production, storage and offloading applications have included the new requirement that the storage tanks be able to handle unrestricted filling with LNG. If membrane-type tanks are used in such new systems, the occurrence of sloshing in the half-load condition becomes one of the most important design issues. In this paper, the authors propose a simple anti-sloshing floating device to be installed inside a liquid cargo tank. By setting the device on the free surface of the liquid cargo, the original free surface is divided into two or more sub-surfaces, and resonant sloshing of the liquid can be avoided by changing the natural frequency of its motion. This floating device can follow the liquid height change in the tank during loading and unloading operations of the liquid cargo, a feature that is especially preferable in FLNG applications. The authors examine the performance of the proposed anti-sloshing device by a series of model experiments and numerical simulations, which indicate that the device's performance is very promising.