A numerical study of the influence of launch parameters on lifeboat deployment from a ship in beam seas

Artikel i vetenskaplig tidskrift, 2006

The process of launching a lifeboat from a ship with no forward speed subjected to beam seas is numerically investigated in this paper. The motions of the ship and the wave conditions are included in the model since they influence the lifeboat's dynamics and its impacts against the hull of the mother ship and water surface. A strip-theory approach is adopted to determine the ship motions, while the total wave condition, which includes the diffracted and radiated wave systems, is calculated using a boundary integral formulation in the frequency domain. The launching process is simulated in the time domain where the influence of such parameters as the position of the launching point, launch velocity, use of fenders on the lifeboat, and time of launch are investigated. Several sea states are considered and, since the wave condition differs between the windward and leeward side, both sides are used for lifeboat launching. The severity of the collisions between the lifeboat and the mother ship are determined by categorizing the resulting accelerations as low, medium, or high. Relative velocities between lifeboat and wave elevation are necessary to determine the water entry process and are consequently calculated. The results from the systematic variations of parameters provide important information to improve the process of evacuating a ship by lifeboat launching.