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.
Study on ship motions and capsizing in following seas. II: Simulation of capsizing
In the interest of brevity, practical equations for ship motion and capsizing in following seas are derived. Simulations of capsizing are carried out by using Tasai's and Inoue's practical formulas for the hydrodynamic coefficients. Finally a material to discuss safety against capsizing is presented for novelty
Dynamic Instability in Quartering Seas: The Behavior of a Ship During Broaching
The dynamic stability of ships encountering large regular waves from astern is analyzed, with focus on delineating the specific conditions leading to the uncontrolled turn identified as broaching. The problem's formulation takes into account motions of the actively steered or controls-fixed vessel in surge-sway-yawroll with consideration of Froude-Krylov and diffraction wave excitation. Dynamical analysis of surf-riding is carried out for the general case of quartering waves, exploring the route periodic motions--surf riding, loss of stationary stability, turn, capsize. Steady-state and transient analysis is carried out in the system's multidimensional state-space in order to identify all existing limit sets and locate attracting domains. Broaching from periodic motions is also a part of the investigation. •.. A minute or two after the reduction of engine speed, and, perhaps, before it had had any significant effect on speed through the water, the ship sheered off to port. The helmsman reported that the helm was hard to starboard, but the ship was not answering. Both engines were then put to full speed ahead, but this order was changed about 13/4 minutes later to full ahead starboard, full astern port. At this point a very severe roll to starboard occurred... The Wahine Disaster, from J. E. CONOLLY, 1972