Free fall lifeboat3/17/2023 ![]() In order to improve the accuracy of the freefall of lifeboat motion simulation in a ship life-saving simulation training system, a mathematical model using the strip theory and Kane’s method is established for the freefall of the lifeboat into the water from a ship. The value of the retardation time in the soft layer model is discussed with relation to the ice crushing by impact. The magnitudes and distributions of the strains are studied depending on the length of the ice plate, retardation time of the ice model, thickness of the plate, shape of the rigid body, place of impact, and the impact speed. It is shown that the strains in the ice plate caused by the impact are weakly dependent on the characteristics of the soft layer. ![]() The rigid body touches the upper surface of the soft layer and then suddenly starts to move downward with constant velocity. The soft layer may describe either the presence of snow on the ice or a layer of crushed ice in the place of impact, or can be considered as a way of regularization of problems with concentrated loads. The reaction force of this soft layer is predicted by a nonlinear and one-dimensional Winkler-Kelvin-Voigt model, which does not permit a contact between the rigid body and the ice plate. The upper surface of the plate is covered with a viscoelastic layer of constant small thickness and negligible inertia. The plate edges are free of bending stresses and shear forces. The ice floe is modeled as a thin viscoelastic plate of constant thickness. The liquid is inviscid, incompressible, and of infinite depth. Two-dimensional vertical impact of a rigid blunt body onto a floating ice plate is studied. ![]() The numerical results were compared with the requirements of the IMO regulations. The Fluid Structure Interaction (FSI) analysis with the penalty coupling method is used for estimating the acceleration response. The new hull form design is proposed and investigated, especially on the acceleration response due to slamming load. The aim of the research is to develop a new type freefall lifeboat for the evacuation system on offshore platform. ![]() The special hull form design should be applied to reduce the acceleration. Since the height of offshore structure to the water surface is significantly high, during the water entry phase the acceleration response of the free-fall lifeboat might cause an injury to the occupants. The international regulations require that a lifeboat for free-fall launching should be able to give protection against impact accelerations when it is launched with its full occupants and equipment from at least the maximum designed height. Freefall lifeboats provide a safe alternative to conventional lifeboats for emergency evacuation from ships and offshore platforms. ![]()
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