Influence of excitation frequency on slosh-induced impact pressures of liquefied natural gas tanks

Liquid sloshing phenomena in No. 2 tank of 140 km³ liquefied natural gas (LNG) carriers have been studied numerically and experimentally. The scale of the model tank was selected as 1/55.9. Roll and pitch motions were tested. For measuring impact pressures, seventeen pressure sensors were installed on the tank model. A large number of excitation frequencies and filling heights were investigated. The experimental results showed that when the frequency of tank motion is close to the natural frequency of fluid inside the tank, large impact pressures may be caused. Resonance frequencies and maximum impact pressures of different filling height were presented. Among all the experimental situations, the maximum impact pressure always occurs at the place near 70% height of tank where should be especially concerned. A computational fluid dynamics (CFD) model was developed to simulate the sloshing in the tank. The model was based on the Reynolds-averaged Navier-Stokes (RANS) equations, with a standard κ-ɛ turbulence model. The volume of fluid (VOF) method was used to predict free surface elevations. Dynamic mesh technique was used to update the volume mesh. Computations for pressure time histories and peak pressures were compared to experimental results. Good agreement was observed.