Liquid sloshing in a baffled rectangular tank under irregular excitations

Sloshing responses in vertical and horizontal baffled tanks under irregular external excitations are investigated by employing a viscous fluid flow model with the Navier-Stokes solver. After the extensive validation of the present numerical model, the numerical experiment reveals many new understandings of the problem. A three-phase variation is suggested to describe the sloshing response under irregular excitations, that is, the first-order natural period controlling stage, the second-order natural period controlling stage, and the transitional stage between them. The sloshing periods are always around the corresponding natural periods with small standard deviations at the first-and second-order natural period controlling stages; while the decreased sloshing periods with large standard deviations can be observed at the transitional stage between them. The sloshing energy concentrated at a single natural frequency or multiple natural frequencies is the major reason for the phenomena. Compared to the results under regular excitations, smaller and larger sloshing amplitudes can be observed in the results of irregular excitations around the resonant and non-resonant frequency ranges, respectively. The normalized sloshing amplitudes calculated from the samplings of the large free surface amplitudes are always smaller than the samplings of the small free surface amplitudes.