This paper describes an investigation of the influence of hydrodynamic damping on the hydrodynamic loads and fluid surface elevations in a ship tank undergoing multiple component motions. A theoretical damping model for horizontal and vertical baffles in the tank has been developed. Experimental measurements of hydrodynamic damping have been carried out to validate the theoretical model, and to investigate the effectiveness of various baffle configurations. It is found that baffles can be used efficiently to damp liquid motions near resonant conditions.
The prediction of hydrodynamic loads on fluid-filled tanks in ships subjected to multiple motions in waves, particularly roll motions, is often an important requirement in design. Significant energy dissipation within the fluid may modify the extent of the sloshing and thus the magnitude of these loads. In particular, energy dissipation may occur on account of flow separation effects as the fluid oscillates past baffles or other obstacles in the tank. Faltinsen (1978) presented a numerical method for studying nonlinear sloshing in rectangular tanks, and modelled the hydrodynamic damping by assuming this to occur at the free surface through a modification to the free surface boundary conditions. Using Faltinsen's approach, Isaacson and Subbiah (1991) obtained a closedform solution for a rigid circular tank with some level of energy dissipation corresponding to a specified damping coefficient. A method for calculating the damping of small amplitude surface waves in a circular tank was given by Case and Parkinson (1958). Viscous dissipation in laminar boundary layers was taken to be the primary cause of damping. Miles (1958) carried out an analysis of the effect of damping in an annular ring on the sloshing oscillations of liquid in a cylindrical tank. The effect of baffles has been considered more recently by Hamlin et al. (1986) and Armenio and Francescutto (1996a, 1996b).
