ABSTRACT:

The paper discusses the experimental results for fluid structure interactions during the slamming impacts. This is a very challenging problem for the wave impacts on the bows or decks, where the slamming forces and hydro elasticity plays a major role in the ship design. Hence, in the present paper experiments were carried out for the hydrodynamic loads acting on rigid bodies striking a horizontal liquid surface at constant vertical speed. The study has been carried out by using a high speed hydraulic shock machine. Three different shapes of the rigid bodies, namely cones, square pyramid and Wedge-cone has been tested and the results shows that the deadrise angle has a high influence on the impact force. The values of slamming coefficient (Cs) have been obtained for all tested geometries. Their parabolic variations with the non-dimensional penetration have been confirmed by the experiments for the cones and the square pyramid. The three-dimensional effect has been shown with the impact of the wedge-cone. The variation of Cs was non linear compared to the standard linear response of the water entry for a wedge. Further, good agreement between theoretical models, numerical results and available experimental measurements has been obtained.

INTRODUCTION

The relative motions between the ships and the water can cause, in very large water impacts on the bows or the decks, severe damage to the ship. An improved understanding of these forces and the parameters involved in such slamming events can lead to better designs and to the development of improved simulation techniques for ship design. Recently the objective is to have larger and high speed vessels which impose a stern shape. This kind of hull form is more often susceptible to the slamming loads, so the structural design considering the slamming impact loads is more necessary.

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