In the present study, liquid sloshing in a 2D membrane-type LNG tank is simulated based on Moving Particle Semi-Implicit (MPS) method, which is a meshless method. However, the traditional MPS method suffers from strong unphysical pressure oscillation. To overcome this, the present MPS employs some improvements, such as: nonsingular kernel function, mixed source term for pressure Poisson equation (PPE) and an accurate surface detection method. Smooth pressure field is obtained based on the present MPS method. The tank is forced to move at various modes: sway and roll motion. The effects of excitation period and amplitude on the flow are investigated. It is shown that the impact behavior is significantly affected by excitation period and amplitude. When excitation period is near resonance period, resonance phenomenon is observed. The flow is violent and a periodic impact behavior shows two large pressure peaks in each period. A case by combining the horizontal, vertical and roll motions is simulated. The predicted pressure on the wall of the LNG tank by MPS method shows a good agreement with experimental data and other numerical results. The impact behavior induced by liquid sloshing is accurately numerically predicted. In addition, violent free surfaces are observed.
Sloshing is a kind of fluid motion in partially filled tank. It is of great importance in design of ships that carry liquid cargo, such as LNG(Liquefied Natural Gas) ship, since the impact load induced by liquid sloshing may cause large damage on the tank and affect the safety of ship. So there is a strong need to predict the impact loads on the structure in design of LNG ship. Sloshing flow is a highly nonlinear problem, which may involve complicated phenomena, such as breaking wave, high-speed impact on tank wall and overturning of free surface.