Sloshing forces on a tank with two compartments, application of the pendulum model and CFD

Two different methods, pendulum model and computational fluid dynamics (CFD), to predict the forces on the ship caused by the flooded water are compared against the model test results. Calculations were performed for a tank in forced motions at different frequencies, for which experimental results were available. The tank had a dividing wall with an opening. The overall behaviour of the force time history was well captured with the pendulum model. In particular at lower frequency the agreement of the force range is very good. Some small force peaks due to the sloshing were predicted in a good correspondence with the CFD simulations. At a higher frequency slight discrepancy is shown also in the CFD calculations. The free surface behaviour is captured in detailed level by the CFD calculations, but the overall motion of the water is captured also with the pendulum model with plane surface model. Comparison to the model tests shows the applicability of the pendulum model in simulating sloshing case with the exchange of water between the compartments. These comparisons show that the pendulum model is a sufficiently accurate and calculation time wise efficient method. It provides a tool to perform a great amount of simulations in order to study the impact of different parameters and the statistical probabilities of ship survival under different accident scenarios.