Effect of roll modelling in beam waves under multi-frequency excitation
Effect of roll modelling in beam waves under multi-frequency excitation
复制标题
DOI：
10.1016/j.oceaneng.2011.07.004
复制
发表时间：
2011-09
影响因子：
5
通讯作者：
G. Bulian;A. Francescutto
中科院分区：
文献类型：
--
作者：
G. Bulian;A. Francescutto
本文描述并比较了三种描述横摇动力学的1自由度模型。两个模型的恢复是非线性的，而第三个模型的恢复是线性的。所有模型都具有非线性阻尼的特点。这两种非线性模型在恢复项和激励项的实现方式上是不同的。一种基于相对角方法的非线性模型，将波浪激励纳入船舶横摇恢复中。第二个非线性模型基于绝对角度方法，将非线性恢复与强迫项分离。比较了三种模型在两种波浪激励下的模拟结果：双频激励和根据规定的海谱产生的激励。在某些情况下，如果恢复的非线性很大，则所考虑的模型的行为显着不同。特别是，相对角度建模中的非线性恢复引入了混频效应，如果横摇恢复非线性足够大，当激励频率远离横摇固有频率时，混频效应似乎也能促进横摇共振运动。
This paper describes and compares three 1-DOF models for the description of roll dynamics in beam waves. Two models have a nonlinear restoring, while the third model is a linear model in restoring. All models are characterised by nonlinear damping. The two nonlinear models are different in the way restoring and excitation terms are implemented. One nonlinear model is based on a relative angle approach, which incorporates the wave excitation into the ship roll restoring. The second nonlinear model is based on an absolute angle approach, which separates the nonlinear restoring from the forcing term. Simulation results according to the three models are compared under two types of wave excitations: bi-frequency excitation and excitation generated according to specified sea spectra. The behaviour of the considered models is shown to be significantly different in some cases if nonlinearities of restoring are large. In particular, the restoring nonlinearities in the relative angle modelling introduce mixing frequencies effects, which seem to be able to promote roll motion at resonance also when the excitation frequency is far from the roll natural frequency if roll restoring nonlinearities are sufficiently large.