LAUNCH AND IMPACT OF FREE-FALL LIFEBOATS .1. IMPACT THEORY

There is a great interest in a practical method of predicting the behaviour of a free-fall lifeboat, when dropped from an offshore platform or from a ship, in order to assess the risk of injury to the occupants. In particular, for those environmental conditions in which full-scale experiments are very difficult, one can benefit from numerical prediction. The hydrodynamic impact of the boat at water entry is a complex problem and makes the establishment of an analytical prediction method a challenging task. This paper proposes a practical method for simulating the water entry of a free-fall lifeboat. The literature on hydrodynamic impact is reviewed and the concepts of momentum balance and added mass are explored by analysing the impact of various cylinders. The theoretical model for the water entry of a lifeboat is derived by extending the concepts for cylinder impact and seaplane landing. A second paper [Boef, W. J. C. (1992), Ocean Engng 19, 139-159] discusses the implementation of the theory and some applications.