Numerical Study on the Effect of Ball Baffles in Reducing Sloshing Loads in Ship Tanks

Abstract

Sloshing is the free surface motion of a liquid in a partially filled container under periodic motion. Liquid sloshing will result in dynamic pressure on the walls of the container causing large deformations to the tank as well as the supporting structures and carrier. This dynamic pressure on the tank walls due to slosh waves are conventionally mitigated in the tanks of very large crude oil carrier (VLCC) ships by means of inbuilt horizontal and vertical baffles which are designed to withstand the worst sea state. However, same designs are adopted even for calm sea states with heavy baffle arrangements increasing the weight of the total structure. Hence, it is essential to introduce an alternative arrangement of baffles in ship tankers which could be altered with varying sea states. The necessity to introduce an effective sloshing reducing baffle which is not of an inbuilt type, is discussed in this study and a suitableness of a ball shaped floating baffle arrangement hereafter referred to as ‘Ball Baffles’ is studied using RANSE based Computational Fluid Dynamics (CFD) simulations. A CFD simulation gives more or less a realistic picture of the physical phenomenon of sloshing in the inner portion of the tanks. The structural deformations of the tank and pressure on the tank walls are also studied with and without ball baffles.