A study on the effect of sloshing on the roll motion of a 2D rectangular box in regular waves

Abstract

The filling ratio of LNG in cargo tanks is continuously changing during the offloading process, which may cause violent fluid motions in the cargo tank. Thus, accurate estimation of the floater's motion including sloshing effects is critical to the safe operation of such structures. The sloshing effect on the roll motion of a two-dimensional rectangular model in regular waves was studied experimentally and numerically. The roll motion was affected by the sloshing in the tank near the sloshing natural frequency as well as the roll natural frequency, but the resonated magnitude was very small. The measured data were compared with numerical results obtained from the multi-modal method. The multi-modal method, both the leading-order solution (Model1) and the next-order solution (Model2), well predicted the roll motion, but it over predicted the roll motion near the sloshing natural frequency. Particularly for the 50%-filled case, the numerical solution of Model 1 became unstable near the sloshing natural frequency, while Model 2 predicted the experiment more closely. For the 10%-filled case, the numerical results of both Model 1 and Model 2 were unstable, which might imply the necessity of another method like the Boussinesq-type method. The numerical result could be improved if the fluid damping is properly increased. This is an abstract of a paper presented at the Proceedings of the Twenty-Second International Offshore and Polar Engineering Conference (Rhodes, Greece 6/17-22/2012).