The safety of occupants in free-fall lifeboats (FFL) launched from a skid is addressed, and the focus is on numerical evaluation of acceleration loads during water impact. This paper investigates the required level of detail when modeling the physics of a lifeboat launch in waves. The first part emphasizes the importance of the non-linearity of the wave surface. Severity of impacts in linear (Airy) waves is compared to impacts in regular Stokes waves of the 5th order. Correspondingly, severity of impacts in irregular waves of the 2nd order is statistically compared to impacts in linear irregular waves. Theory of the two wave models are also briefly presented. The second part discusses the importance of a more detailed modeling of the launching system. This concerns especially cases for which damage to the mother vessel induces major lifeboat heel angles. A three-dimensional skid model is presented, along with validation against experimental measurements. In addition, the wave induced motion of the mother vessel is included. Consequences on the severity of the impact of the lifeboat in regular waves are discussed. This study is based on MARINTEK’s impact simulator for free-fall lifeboats, in which slamming loads are evaluated based on momentum conservation, a long wave approximation, and a von Karman type of approach. It is coupled here to the SIMO software, also developed at MARINTEK. Performance of this coupling is discussed.
- Ocean, Offshore and Arctic Engineering Division
Computing Acceleration Loads on Free-Fall Lifeboat Occupants: Consequences of Including Nonlinearities in Water Waves and Mother Vessel Motions
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Luxcey, N, Fouques, S, & Sauder, T. "Computing Acceleration Loads on Free-Fall Lifeboat Occupants: Consequences of Including Nonlinearities in Water Waves and Mother Vessel Motions." Proceedings of the ASME 2010 29th International Conference on Ocean, Offshore and Arctic Engineering. 29th International Conference on Ocean, Offshore and Arctic Engineering: Volume 2. Shanghai, China. June 6–11, 2010. pp. 297-304. ASME. https://doi.org/10.1115/OMAE2010-20329
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