Research On Intact Stability Of A Catamaran In Waves

The ship stability is one of the most important ship performances.With the development of shipbuilding industry,ship stability can no longer be limited to the stability rules based on empirical data statistics,at the same time,the check condition of the hydrostatic sea state can not satisfy the development status of ship types with rich sea conditions.In 2008,the IMO developed a new generation of stability standards that is in order to meet the needs of development,and the first two levels of the draft of the three failure modes,such as the paralysis of the ship,the rolling of the parameters and the loss of pure stability,have been preliminarily formed.In fact,catamaran ship because of its ship form characteristics,has a large stability reserve,in the military and civilian ships have important application value.According to the actual project needs,this paper studies an experimental catamaran with a higher superstructure under high sailing sea conditions,compared with the stability of the ordinary catamarans,the stability change of the experimental catamaran under the wave is more complicated.Therefore,the study method of this paper is based on the second generation stability standards to analyze the stability of a catamaran under waves and the influence factors of stability were also studied.To this end,this paper has done the following work:The equilibrium of the longitudinal and vertical forces and moments are established based on the two-dimensional potential flow theory.And according to the transformation relation and the interpolation between the fixed coordinate system,the motion coordinate system and the inertial coordinate system the instantaneous intersection coordinates of catamaran and regular wave are obtained.By using the Green formula to calculate the integral of the closed curve,the area of the section and other section elements are obtained.Then,the displacement volume of the catamaran and the position of the center of buoyancy can be obtained through the integral of the master.Finally,based on the F-K hypothesis,the ship righting arm curve is obtained,and the initial stability of high GM,the stability of the vanishing angle and other related curve elements are as output.The radiation force and diffraction force in the transverse direction of the transverse motion,and the radiation moment of the rolling direction and the diffraction moment are superposed based on the three-dimensional potential flow theory and the three-dimensional panel method.And then become the total moment of radiation and diffraction force.Composing the resilience of the main wave forces obtained by programming in the previous chapter and the total torque as a linear superposition.On the basis of this,the change of the complex force time series is studied,and the influence of different ship form factors and environmental factors on the change of the total force in the regular wave is analyzed.Combined with the stability evaluation project of an experimental catamaran,using the first layer of the wind heel stability and the first layers of parametric roll and pure stability loss in second generation stability criterion to carry out the sensitivity analysis of different catamaran samples.The stability of the catamaran with different superstructure designs is calculated and analyzed,and then the optimal design scheme is given.