The work presented in this paper deals with the analysis of the roll motion of ships with free surface liquids on board. A mathematical model for the evaluation of the ship rolling motion has been developed. It consists of the matching of the standard uncoupled roll motion equation with the Reynolds Averaged Navier-Stokes equations for the simulation of liquid sloshing inside the partially filled tank. Some discussions on the problems which can rise when the above matching is performed are reported. Numerical runs have been carried out considering two different tank geometry, a rectangular unbaffled tank and the same provided with a vertical baffle put on the bottom of the tank. In order to validate numerical results experimental tests have been carried out in regular beam sea at the Towing Tank of the Hydrodynamic Laboratories of D.I.N.M.A. The main pecularities of the dynamic system have been evidenced. When an unbaffled partially filled tank is analysed the system can be regarded as a lightly damped two-degrees of freedom dynamic system and a two-peak roll response in the frequency domain is evidenced. When a baffled configuration is studied. depending on the natural damping of liquid sloshing inside the tank. the two-peaks response can be loose. Anyway it has been observed that the presence of a vertical internal baffle provides a strong reduction of the roll angle as compared to the unbaffled geometry in the whole cases investigated. Discussions on the mathematical and physical features of the problem investigated are also reported.


One of the challenges of near future as concerns maritime transportation is constituted by the improvement in RO-RO safety. This is indeed essential also for the survival of this ship concept. After the last accident, the sinking of Estonia, panels have been formed in the frame of SNAME (Hutchison, 1995) and IMO (IMO News, 1995) for studying the problem.

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