is subjected to the gravitational force due to the propulsive acceleration, and 2) the case in which separation of the slosh eigenfrequency is caused by the Coriolis force. For the first case, it is shown that the mechanical models in the two orthogonal directions in which the breadth of the liquid surface is maximum and minimum may exhibit difference for low liquid-filling levels. In the second case, a two-directional mechanical model is developed by taking into account the interaction between the slosh motions in the two orthogonal directions.