Models for Fluid-Structure Interaction in Liquefied Natural Gas Sloshing

Abstract

The energy transition requires the maritime industry to shift to a different fuel. A long term solution is liquefied hydrogen, but there are many challenges to get there. On the short term liquefied natural gas (LNG) might be the most feasible option, because its use relies mostly on existing technologies. It is however not straightforward to take the design of an LNG tank used for cargo and implement it on a containership. The tank is not just a hold in the ship, but it is insulated with a specific cargo containment system (CCS). A CCS is typically made up of many layers, metal membranes to keep the LNG in, foam to provide insulation and plywood layers to provide enough strength. When the cargo tanks are scaled to meet the size requirements of a fuel tank, the fluid will behave differently and physics of load and response inside the tank scale as well. This means that with scaling the dominant loading mechanism on the tank walls changes. Simply scaling the CCS along with the hold dimensions is therefore not a safe choice. The current strength assessment of the tanks uses tuning factors that are based on experience with a specific size of LNG tanks. Most uncertainty in scaling is about the validity of the method considering variablity of the impact, phase transition and fluid-structure interaction (FSI). This thesis focusses on the fluid structure interaction of the CCS with the liquid within the cargo tank, both from a fundamental perspective and by looking at the wave impact on the tank walls…