Transient Dynamic Responses of an Internal Liquid-lng Tank-sea Water Interaction System Excited by Waves and Earthquake Loads

Sloshing problems in partially filled large LNG carriers are of increasing concern because sloshing loads may endanger LNG carriers in operations. Currently, most investigations on sloshing problems mainly focus on the analysis of liquids in rigid tanks which omitted fluid-structure interactions. Based on a mixed displacement–pressure finite element method developed, the authors recently investigated the natural vibration of an internal liquid–elastic structure–external water interaction system. The simulation demonstrated the significance of the interactions between internal liquid sloshing modes and floating modes of LNG tanks on the external sea water. This paper further studies the dynamic responses of this integrated system subject to sea waves and earthquake excitations. The sea wave loads are modelled by pressure waves with different frequencies applied to a boundary of the external water domain and the ground motion data recorded from El-Centro earthquake is used as an earthquake load to the system. The numerical analysis on the dynamic responses of this coupled system further confirms the necessity to consider fluid-structure interactions for safe LNG ship designs.