Hydrodynamic simulation of frontal plane deck motion during a mechanical shock on a lifeboat

Abstract

Multi-axial repeated mechanical shocks presented in the frontal plane of any planing crafts during sea transits impose an increased risk to injury for occupants. However, understanding of the abrupt motion in this plane is seldom documented in adequate detail. With the help of computational fluidic dynamics (CFD) software, the study simulates the boat motion during different water entry conditions. An Atlantic 21 lifeboat is dropped into water with different drop heights and entry roll angles in simulation. The vertical, lateral and angular roll acceleration of the lifeboat are derived from the CFD simulations. The vertical acceleration calculated at a crew seat is considerably higher than that at the boat centre of mass (CoM) in the frontal plane. The percentage increase from the offset position relative to the CoM is primarily governed by the entry roll angle with little influence from the drop height. The lateral acceleration is less critical when assessing mechanical shocks in the frontal plane, as it is largely cancelled by the lateral component due to the offset and the roll angular acceleration.