An Investigation on Two-Dimensional Nonlinear Sloshing in Rectangular Tank

Two-dimensional liquid sloshing in rectangular tank of FLNG system is investigated both numerically and experimentally. In numerical simulation, a time-domain scheme has been developed based on potential flow theory in boundary element method. Tank movement is defined by wall boundary condition to produce a reciprocating oscillation. Nonlinear free surface condition is adopted to capture free surface elevation. Energy dissipation caused by viscous effects is considered by applying artificial damping term to the dynamic free surface condition, which is also vital to achieve a steady-state solution. For comparison, experiments of a rectangular tank filled with water subjected to specified oscillation are carried out. As coupling effects between sloshing and tank motion is not included in this research, the testing apparatus is required to produce consistent oscillation movement and not affected by the change of filling condition and sloshing load. Liquid surface elevations in several typical places of the tank were measured. Sloshing related parameters including oscillation amplitude, frequency and filling level are analyzed systematically. It’s found that numerical simulation results have good agreement with phenomenon observed under small amplitude excitation, and this nonlinear analysis method is proved to be effective in capturing liquid surface elevation. It is found that sloshing in tank is sensitive to filling level as well as excitation frequency, especially in the crucial combination cases of them. For given filling level, sloshing tends to be violent near corresponding natural frequencies, and viscous damping has limited contribution to sloshing amplitude when resonance occurs. This fundamental investigation also paves path for the study of more complicated sloshing problems.