风作用下缆船拖带非线性系统运动数值模拟

基于船舶操纵性运动方程和拖缆的三维动力学运动方程,提出了被拖点位置匹配的方法,建立了拖船—拖缆—被拖船系统的非线性整体拖带动力学模型.为了考察被拖船航向稳定性与横向稳性的关系以及风载荷作用的影响,被拖船采用水平面四自由度运动方程,并引入了风的作用力和力矩.拖船采用PD控制方法较真实地模拟了拖船航向改变的运动过程.对一个拖船—拖缆—被拖船系统(5 000 t的拖船和3 000 t的被拖船)在时域内进行了风作用下拖带运动的模拟.计算结果表明,风力增大拖带航向稳定性降低,拖带航向稳定是横向稳的必要条件.数值计算结果归纳出判别被拖带船航向稳定性的极坐标图,该极坐标图表明顶风航行较顺风具有较强拖带航向稳定能力,但是拖带航向稳定性区域很小,而顺风和顺斜风拖带比顶斜风具有更大的拖带航向稳定性区域.

The nonlinear dynamics model of towed cable-ship and numerically simulation

Based on the equations governing the motion of the ship and three dimensions equations of the towed cable system,the nonlinear towing system dynamics model of towing ship and towed ship connecting with cable were established by matching both positions of towed point of ship and end point of cable.To evaluate the relationship between the course stability and the transverse stability of towed ship,the four degree equations of towed ship were used in the towing system dynamics model.In order to research the influence of wind action on the motions of towed ship,the wind action force and moment to the ship were also introduced.The towing ship motion was also simulated by steering rudder using the control rule of PD,so the motion of towing ship under steering rudder was calculated truly for simulation.For one towing system which is connected by towing cable and consisted of one towing ship with 5000 tons and one towed ship with 3000 tons,their motions were simulated by using the nonlinear towing system dynamics model.From results of the simulation,it can be concluded that inorder to keep the transverse stability of towed ship,the course stability of towed ship must be kept.Polar coordinates of evaluating the course stability and wind power,wind heading were obtained for the simulating,which shows the towed ship has more course stability under head wind,but has more course stability scope under tail wind.