Numerical study of porous material layer effects on mitigating sloshing in a membrane LNG tank

Severe sloshing in a membrane-type liquefied natural gas (LNG) tank excited by random sea wave easily causes overturning of liquid cargo ship and structural damage of tank. Besides the baffles, maybe the porous material layer pasted tight to the inner periphery of the tanks is another way to mitigate sloshing and reduce potential risks caused by severe sloshing. The computational fluid dynamics (CFD) code OpenFOAM was employed to study sloshing wave interaction with porous material layer. The improved IHFOAM used to simulate porous breakwater was validated against with available experimental data, good agreements are obtained. Three intrinsic parameters of porous material layer such as porosity (n), thickness ratio (w/a), and average diameter ratio (D-50/w) were varied to obtain optimized parameters in mitigating sloshing by conducting two-dimensional numerical tests, and the corresponding critical value that reduced sloshing dynamics pressure at utmost was found. The tank with optimized porous material layer manifested well in mitigating sloshing in comparison with the case with solid vertical baffle. Finally, the optimized porous material layer was installed around the inner periphery of the membrane-type LNG tank excited by both regular and irregular excitation to discuss effects of porous material layer on mitigating sloshing under extreme conditions.