The modeling of ship behavior in astern seas requires a large range of maneuverability and seakeeping knowledge since the understanding of the ship motions returns to solve a fluid structure interactions problem between waves and the ship hull. The broaching phenomenon is known as an abrupt change in motion in the horizontal plane, resulting in a loss of ship’s heading. It is characterized by a sudden divergence of yaw. Thus, there is a transfer of the kinetic energy on the roll axis that increases the risk of ship capsize. In the aim of modeling this phenomenon, the developed model uses the capture of the intersection between the ship hull and the free surface. Thus, we can overcome the hydrostatic stiffness matrix and integrate directly the hydrostatic pressure on the immersed surface. This method has the advantage of taking into account non-linearities of the wave profile into the calculation of the immersed surface, directly by performing a remodeling of the facets near the free surface. In the literature, three main factors are likely to affect the stability: the loading of the vessel, the presence of external disturbance torques and inadequate conditions of navigation, as is the case when a ship is caught in a storm. The first two factors are taken into account in the study of static stability, while the third factor is considered in the study of the instantaneous stability. Hydrostatic behavior of a ship is interesting when one wants to know her intact stability limits in calm seas. However, in the study of the ship behavior in following seas, the ship is no longer in usual conditions of navigation, but in unsuitable conditions requiring the study of the instantaneous stability. In the model formulation, the dynamic torsor comes from the general non-linear maneuverability equations and the time advance is solved by a 4th order Runge Kutta scheme with a constant time step. The torsor of the total applied mechanical action on the ship hull is expressed as the superposition of six torsors (gravity, hydrostatic, Froude Krylov, radiation, hydrodynamics and maneuverability) expressed in the center of gravity of the ship. Thus, we obtain a strong coupling between the maneuverability and seakeeping equations. Validation cases will be conducted and presented. The improvement of the model will require the implementation of test campaigns that will be specific for the study of ship behavior in astern seas. Validation of the model will help to define new stability criteria for ships in wave.
Existence and stability of a capillary free surface appearing in dewetted Bridgman process. I.
