This paper is Volume 4 of the ISOPE-2009 paper "Optimization of LNG tank shape in terms of sloshing impact pressure" and focuses on an innovative modelling approach of elastic tank walls. This approach is based on finite particles, which provide similar properties as finite elements in classical structure mechanics. It is implemented into a computationally efficient numerical multi-body simulation program, which is flexible in geometry and dynamic load spectrum. It features a particle-based liquid model and provides time accurate hydrodynamic pressure results in three dimensions and 6 Degrees-of-Freedom. Based on the results of specific tank geometries using a rigid wall model, unsteady sloshing loads are computed for elastic tank walls. The stresses and strains are discussed to optimize the structure in terms of impact pressure loading. Thereby, the LNG tank geometry is flexible in terms of wall friction, elasticity laws and damping coefficients. A special focus has been set on the feasibility and production issues of an advanced lightweight tank made of hybrid composite materials. The coupled LNG-structure dynamics is analyzed using classical laminate theory in order to provide some recommendations for a possible structural layout.
The Liquefied Natural Gas (LNG) provides an efficient way for long distance transport in large vessels. The gas is cooled down to extremely low temperatures such that it can be transported in the liquid state. Hence, the liquefied gas obeys the laws of liquid dynamics. During the filling process, the LNG exercises unsteady forces on the tank walls and makes the vessel react to these forces by ship motion. The ship motion, however, is the driver for LNG sloshing in the tank. Special focus is given to the tank shape to minimize the impact pressure from sloshing LNG, see Fig. 1. Sloshing in partially filled tanks is a complex physical process.
