Green Water Loads on a Cruise Ship

A linear boundary-element method and a Reynolds-averaged Navier-Stokes (RANS) equations solver were combined to predict maximum green water loads on a typical cruise ship of medium size. For structural analysis, a one-way coupling mapped the hydrodynamic pressure from the finite-volume grid onto the computational structural dynamics finite element mesh. First, linear long-term maximum ship responses were determined by a boundary element method combined with long-term statistics based on spectral methods; transfer functions of these responses were used to define response-conditioned wave trains inducing the linear long-term maximum ship response. The investigated wave sequences were correlated to a dedicated probability level for a lifecycle time of 20 years in the North Atlantic environmental wave conditions and for a ship speed of six knots.Critical impact locations were found to include the weather deck in the foreship, the front wall of the superstructure and the overhanging bridge deck. Predicted loads were compared to experimental data obtained in conditioned wave trains and in extreme irregular sea states. Numerical and experimental results revealed significantly higher loads than design loads specified by classification society rules. Pressure peaks on the weather deck and the superstructure front wall were comparable to rule-based design pressures for breakwaters on containerships and exceeded pressure peaks on the bridge deck.Copyright © 2013 by ASME