Simulation of sloshing effect on vessel motions by using MPS (moving particle simulation)
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The coupling and interactions between vessel motion and inner-tank sloshing are investigated by a potential-CFD (Computational Fluid Dynamics) hybrid method in time domain. Potential-theory-based 3D diffraction/radiation panel program is used to obtain the hydrodynamic coefficients and wave forces for the simulation of vessel motion in time domain. The liquid sloshing in tanks is simulated in time domain by using the improved Moving Particle Simulation (PNUMPS) method and it is validated through comparison against sloshing experiments. The calculated sloshing tank forces and moments are applied to the vessel-motion simulation as excitation forces and moments. The updated ship motion, which is influenced by sloshing-induced tank forces, is in turn inputted to the MPS system as forced motions. For the verification of the coupling, a barge-type FPSO hull with two partially filled inner tanks is selected and the numerically simulated results correlate well against the measurements done by MARIN for various fill ratios. It is seen both in prediction and experiment that the roll RAOs(Response Amplitude Operators) are sensitive to the amount of liquid cargo and can be increased by a factor of 2 or 3 in some wave frequency range compared to the bare-hull or rigid-cargo cases. It is also shown that the nonlinear sloshing effects can alter the vessel-motion characteristics in relatively high waves with the peak period close to sloshing natural frequencies. Copyright 2011 Tech Science Press.
