In this paper, the possibility of obtaining an efficient description of the roll motion of a ship with liquids with free surface on board is discussed in detail. Available mathematical models with concentrated parameters are implemented and compared with scale model experiments. Critical points are evidenced by using a high efficiency Parameter Identification Technique. Finally a model with good simulation capability is presented. The proposed mathematical model fits well the experimental data requiting the estimation of a reduced set of parameters. The method appears of great interest in the frame of current research on the damaged ship behaviour.
Since the early papers of Van der Bosch and Vugts (1966) and Van der Bosch and Zwaan (1970) and even earlier with the work of Watts (1883,1885), the attempt to derive an appropriate mathematical model for the solution of the problem of the ship rolling with a partially filled tank on board has been attracting many researchers in the field of Naval Architecture. This is still an up-to-date task especially as regards the modelling of water inflow/outflow after damage. In Aeronautical Engineering the problem of the route stability of missiles and aircrafts with a free surface tank was also considered a problem of primary importance (Abramson, 1966). In the work of Van der Bosch et al. (1966) the main idea was to modify the traditional roll motion equation by simply adding the sloshing moment in the RHS of the equation as an additional exciting moment. The latter had to be evaluated experimentally from measurements on an isolated tank forced in a sinusoidal motion. By this approach the inherent complexity of developing a suitable mathematical modelling of the liquid motion in the tank could be avoided at the cost of large campaigns of experimental measurements.
