斜浪群波中船舶复原力和参数横摇研究

Study on roll restoring variation and parametric rolling in oblique group waves

为研究斜浪群波中船舶参数横摇及其与复原力变化的关系,基于切片理论,计算了船舶无横倾时在斜浪群波中时间序列垂荡和纵摇运动,确定出波面与船体的相对位置.利用3个坐标系之间的转换关系,求解斜浪群波中船体各横剖面左右舷与波面的交点,确定各浸水剖面瞬时湿面积.基于规则波中复原力计算公式,提出了Froude-Krylov假说下的群波中复原力计算方法.同时,利用作用在横倾船舶上的辐射力和绕射力,求出斜浪群波中船舶复原力之辐射力和绕射力部分.在复原力计算的基础上,确定一个参数横摇模型,实现斜浪群波中参数横摇计算.以一艘集装箱船为例,研究了斜浪群波中复原力变化以及参数横摇规律,结果表明斜浪群波中会发生参数横摇现象,且复原力变化幅度是影响参数横摇预报的一个重要因素.

In order to study parametric rolling and its relationship to roll restoring variation in oblique group waves,first,the relative position of a ship to oblique group waves was determined with heave and pitch motions obtained by a strip theory applied to an upright hull.Secondly,a general method for calculating intersections between ship and oblique group waves was presented based on transformation of three coordinate systems.The instantaneous area of wet sections was calculated,and then the nonlinear Froude-Krylov component of restoring variation in group waves was presented based on that formula in regular waves.Thirdly,radiation and diffraction components were taken into account by using radiation and diffraction forces acting on a heeled hull.Then a mathematical model for parametric rolling was developed based on the calculation of restoring variation.Finally,restoring variation and parametric rolling of a container ship in oblique group waves were studied and it was found that parametric rolling could occur in oblique group waves while roll restoring variation is an essential part of parametric rolling prediction.