Two numerical models, a CIP (Constrained Interpolation Profile) based method and a MPS (Moving Particle Semi-implicit) method, which have been developed and improved in RIAM, Kyushu University for years, have been used to simulate the sloshing flow of liquid in a two-dimensional tank. The purpose of this research is to validate the CIP based method and the MPS method against experimental data with a rectangular tank. The tank is subjected to rolling motions. The transient behavior obtained from the simulation is compared to the experimental observation. Discussion is made on the features of these two numerical models for such tank sloshing problem.
Liquid cargo carriers usually operate in partially filled conditions. When those ships are oscillating in waves, the liquid inside the tank responds and sloshing occurs. In some cases, sloshing forces acting on tank structure can be large enough to cause local structural deformation or damage. Moreover, in recent years the size of membrane-type LNG tanks is increasing due to the demand for larger payload of this kind of ships. As a result, the difference between ship motion excitation frequencies and tank sloshing natural frequencies is decreasing; and the rate of occurrence of structural failures due to sloshing is therefore expected to rise in future. Violent sloshing is a strongly nonlinear problem, which may involve complicated hydrodynamics phenomena such as high-speed liquid impacts on tank walls, breaking waves, jets, liquid droplets formation and air bubbles entrainment. Theoretical analyses on the liquid sloshing are generally limited to linear problems. Experiments have been the most important source of practical information about violent sloshing. However, high cost and small scale are the obstacles for obtaining necessary information by experiments. CFD simulations are becoming more and more important in violent sloshing studies. Numerical approach may be the only practical research tool capable of full-scale predictions.
