A numerical study on sloshing mitigation by vertical floating rigid baffle

Abstract

Due to large hydrodynamic loads generated by the violent free surface flow, sloshing in partially filled tanks is an important phenomenon for the design of several offshore structures such as FPSO platforms, LNG carriers, crude oil carriers and, more recently, FLNGs. This study is focused on the numerical investigation of sloshing mitigation devices based on a floating baffle. For this purpose, the complex and highly nonlinear sloshing phenomenon is modeled and simulated using the Moving Particles Semi-Implicit (MPS) method, which is a fully-Lagrangian particle-based method for the simulation of incompressible flows widely applied to the study of fluid–structure interaction phenomena involving large free surface deformations, fragmentation and merging. As a reference for an in-depth discussion, the effectiveness of the equivalent fixed baffles placed at the bottom, the ceiling and mid-height of the tank were also studied. This work is divided into three parts: (1) the validation of the numerical method, (2) the study on the effect on sloshing of fixed baffles placed amid-tank and at different heights and (3) the investigation of the sloshing mitigation performance of floating baffles with a degree of freedom in the vertical direction of the tank. The effects of the floating baffles densities, which influence the draft of the baffles, on sloshing are investigated as well. The use of fixed baffles provided effective sloshing mitigation at the resonant frequencies for certain filling conditions depending upon the location of the baffle, but it might lead to even more violent flows in other filling conditions. On the other hand, the floating device presented sloshing mitigation for a larger range of filling conditions. Moreover, four different patterns of resonant motion of the floating baffle were identified and simple analytical estimations that could predict corresponding natural frequencies were proposed herein.