ABSTRACT

Catamarans are increasingly used for high-speed transportation of passengers because of the advantages offered in terms of stability and large deck area. To achieve high speeds the hulls of the catamarans are made quite slender. This slender shape helps in reducing the slamming loads acting on these hulls. However, slamming loads of considerable magnitude can act on relatively flat cross structures and this is referred to as "wet deck slamming". Knowledge, nature and magnitude of the wet deck slamming loads are important for the design and safety of these crafts. This paper presents a numerical approach to predict slamming loads acting on catamaran sections, accounting for the flow in the longitudinal direction during impact. Results are presented for the free surface contours at different time instants along with the pressures and force histories acting on the hull and the cross structure for a range of impact velocities.

INTRODUCTION

Computational Fluid Dynamics (CFD) is increasingly being applied to ship hydrodynamics with the decrease in cost of computing resources, increase in computing power and the advent of better numerical methods. One of the important problems in ship hydrodynamics is the prediction of slamming loads to a good degree of accuracy. These loads are non-linear and as a result of slamming large impulse pressures act on the hull over a very short period of time. These pressures can cause structural damage to the hull. The impulse nature of slamming loads makes them difficult to measure experimentally (Gatiganti et al., 1998). Numerical methods have been successful in treating the two-dimensional water entry problem with some success (Zhao and Faltinsen, 1993), (Arai et al., 1994) and (Gatiganti, 1997). The application of this method to the structural design of a fast monohull has been presented (Gatiganti and Kuo, 1997).

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