Study on ship's stability loss in surf-riding based on CFD
Based on Computational Fluid Dynamics, ship's righting arms of different heeling angles were calculated to study ship's stability loss in following sea. First, based on the wave-generation method of defining inlet boundary conditions, the numerical wave tank was constructed for ship's movement in surf-riding. Second, one slender ship's flow filed in calm water was numerically simulated, and the righting arms of different heeling angles were calculated. Third, the slender ship was set to navigate in surf-riding with wave crest at the midship section, and the flow field was simulated to get the righting arms of different heeling angles. The simulation results indicate that the righting arm in calm water show good agreement with experiment data; the stability loss is more serious when the wave amplitude is bigger; and ship wave's effect cannot be neglected in calculating ship's stability loss in surf-riding when ship speed is high.
CALCULATION OF THE RIGHTING ARM FOR SHIPS IN QUARTERING SEAS
A new method for calculating the righting arm of ships in quartering seas is presented. Righting arm curves for different ship- wave related positions are calculated for four ships. The effect of wave height and wave length on the righting arm is discussed. Finally, a captive model test was carried out to measure the ship heeling moment in quartering seas. The experimental results are consistent with those obtained by calculation.
Ship Capsizing as a Nonlinear Dynamics Problem
Almost one hundred total losses per year of ships greater than 500gt are registered by the Institute of London Underwriters, (Underwriters, 1997), Fig. 1, however, only the very big disasters enter the view of the public. Lost ships mean economical losses and environmental risks. But these disasters are primarily painful because they take human lifes. That is why the number of total losses has to be reduced.