Natural dynamic behaviour of an integrated liquid – LNG tank – water interaction system

Xiong, Y.P. and Xing, J.T. (2007) Natural dynamic behaviour of an integrated liquid – LNG tank – water interaction system. MARSTRUCT 2007: 1st International Conference on Marine Structures: Advancements in Marine Structures, Glasgow, United Kingdom. 12 - 14 Mar 2007. pp. 313-321 .

Abstract

A previous investigation of sloshing in liquid-container interaction systems has shown that sloshing frequencies of the liquid are almost not affected by structures having a first natural frequency much higher than that of the liquid sloshing frequencies. However, for large and more flexible tanks as occur in LNG ships, the floating frequencies of the ship are normally of a similar low value to the sloshing frequencies of the liquid in a tank. Therefore, the coupling between the sloshing liquid, the floating structure and seaway is of importance in characterising the dynamic behaviour of the complete system. In this paper, an integrated liquid – LNG tank – water interaction system is numerically investigated. It is shown that complex coupling mechanisms exist within the overall integrated system. To illustrate the findings six cases are studied. Namely, 1) liquid sloshing in a fixed rigid tank, 2) sloshing of external water, 3) elastic tank only, 4) internal liquid-tank interaction, 5) elastic tank- external water interaction and 6) internal liquid-elastic tank-external water interaction. The natural frequencies and the corresponding vibration modes of this complex coupled system are obtained and these numerical results provide an insight into the complex dynamic behaviour of the integrated interaction system. The guidelines proposed may be of use for the dynamic design of LNG carriers to ensure safety whilst operating in a rough seaway.

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Contributors

Author: Y.P. Xiong

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