As part of the ISOPE 2009 sloshing comparative study, the eight specified test problems are analyzed using the CFD code CFX-11. The computational models and meshes are based on the methods developed in previous studies. 20 oscillations are simulated for each case and the mean, maximum and the mean of the 1/10th highest pressures are computed for each specified pressure sensor. The flow features and their influence on the impact pressure magnitude are then considered and both hydrodynamic impacts and impacts with air entrapment are observed. It is found that the peak pressures are up to 170 kN/m2, with time durations of the order of one millisecond. The resolution of such small time scales and the occurrence of wave breaking and air entrapment, which influence the pressure significantly, require a robust multiphase model capable of simulating phase mixing.
Sloshing occurs when a tank is partially filled with a fluid and subjected to an external excitation force (Olsen, 1976). Ships with large ballast tanks and liquid bulk cargo carriers, such as very large crude carriers (VLCCs), are at risk of exposure to sloshing loads during their operational life (Rizzuto and Tedeschi, 1997). The inclusion of structural members within the tanks dampens the sloshing liquid sufficiently in all but the most severe cases. However, this approach is not used for Liquefied Natural Gas (LNG) carriers and the accurate calculation of the sloshing loads is an essential element of the LNG tank design process (Bass et al., 1980; Knaggs, 2006). Recent increases in vessel size have renewed interest in methodologies for the simulation of the sloshing loads experienced by the containment system (Han et al., 2005; Card and Lee, 2005). Recent incidents of sloshing damage onboard LNG carriers (Hine, 2008) have added further urgency to the improvement of sloshing analysis techniques in LNG carrier and floating LNG design.
