The two-layer sloshing of water and diesel oil is studied numerically by using the Consistent Particle Method (CPM). CPM solves the Navier- Stokes Equations through the two-step projection scheme. Compared to other projection-based particle methods, the distinct feature of CPM lies in its consistency and high-order accuracy in computing the spatial derivatives. By studying an experimental benchmark case, the capability of CPM in modelling large-amplitude two-layer sloshing and reproducing a clear fluid interface is demonstrated. Using the validated model, the two-layer sloshing under sway-only and coupled sway-heave excitations are studied. For the coupled excitation case, it is found that the sum or difference of the sway and heave frequencies being close to the odd multiple of the system's natural frequency induce secondary violent sloshing waves even both excitations are further away from the natural frequency.


With the global shortage of resources, the demand for liquefied natural gas (LNG) keeps growing and by 2035 the gas is projected to supply the largest share of energy demand growth and over 40% of growing demand (Shell 2019). Compared to the traditional LNG system, the FLNG (floating liquefied natural gas) facility integrates the production, storage, processing, and transportation, and hence saves the gross cost. Therefore, the FLNG is getting more market share in the LNG industry. The integrated capability of FLNG in production and storage also implies that the filling level in an FLNG tank can vary from very shallow to very high. Previous studies on sloshing have suggested that the wave impact pressures and loads induced by middle-filling sloshing can be very violent (Luo et al. 2020), which may cause local damages to tank structure (Wang 2010) or global instability to the ship (Luo et al. 2016). For the safe design of FLNG vessels, therefore, the sloshing waves in FLNG tanks especially the resonant scenarios in middle filling levels need to be thoroughly investigated.

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