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This study investigates the roll decay of a fishing vessel by experiments and computational fluid dynamics(CFD)simulations. A fishing vessel roll decay is tested experimentally for different initial roll angles. The roll decay is also simulated numerically by CFD simulations and is validated against the experimental results. It shows that the roll damping could be obtained by CFD with high level of accuracy. The linear and nonlinear damping terms are extracted from the CFD roll decay results and... 相似文献
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为提高船舶横摇运动预报的精度以及实时性,提出一种利用混沌理论和最小二乘支持向量机(Least Squares Support Vector Machine,LSSVM)在线训练算法的实时在线预报方法。针对预报模型的固定核参数不能适应横摇运动的动态变化而进行自动调节这一问题,设计一种基于LSSVM的变参数在线建模方法。利用三个LSSVM并行建模,将整个预报过程分为初始阶段和若干个预报阶段,并在每个阶段末选出下一个预报阶段的预报LSSVM,同时根据启发式规则为另两个LSSVM设定核参数,它们作为下一阶段的比较LSSVM。对某船横摇运动时间序列进行预报,仿真结果表明,所提变参数LSSVM在线预报方法平均相对均方误差为6.85%,相比于固定参数预报方法具有更好的适应性。 相似文献
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船舶参数激励非线性横摇运动方程 总被引:3,自引:0,他引:3
讨论了船舶在海浪上运动时参数激励产生的机理,建立了船舶参数激励和波浪激励非线性横摇运动方程。本文工作为研究倾覆机理奠定了基础。 相似文献
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随机波中船舶参数横摇研究 总被引:2,自引:0,他引:2
针对随机波中船舶参数横摇,提出一种数值预报方法。采用新的随机波成形方法,求解出船舶无横倾时在随机波中时间序列垂荡和纵摇运动,确定出船-波相对位置。利用3个坐标系之间的转换关系确定船体各横剖面左右舷与波面瞬时交点,然后对波浪压力沿船长湿表面积分,得出船舶复原力的Froude-Krylov部分。提出复原力之辐射力和绕射力部分和横摇角的非线性假定。确定一个参数横摇数学模型,实现随机波中参数横摇计算;通过试验和数值模拟对一艘巴拿马型集装箱船进行了参数横摇预报,研究了随机波中参数横摇的实际非各态历经的特点。 相似文献
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《船舶与海洋工程学报》2020,(1)
This study aims to investigate the nonlinear added mass moment of inertia and damping moment characteristics of largeamplitude ship roll motion based on transient motion data through the nonparametric system identification method. An inverse problem was formulated to solve the first-kind Volterra-type integral equation using sets of motion signal data. However, this numerical approach leads to solution instability due to noisy data. Regularization is a technique that can overcome the lack of stability; hence, Landweber's regularization method was employed in this study. The L-curve criterion was used to select regularization parameters(number of iterations) that correspond to the accuracy of the inverse solution. The solution of this method is a discrete moment, which is the summation of nonlinear restoring, nonlinear damping, and nonlinear mass moment of inertia. A zero-crossing detection technique is used in the nonparametric system identification method on a pair of measured data of the angular velocity and angular acceleration of a ship, and the detections are matched with the inverse solution at the same discrete times. The procedure was demonstrated through a numerical model of a full nonlinear free-roll motion system in still water to examine and prove its accuracy. Results show that the method effectively and efficiently identified the functional form of the nonlinear added moment of inertia and damping moment. 相似文献
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从概率的角度探讨不规则波中船舶参数横摇的特性。参数横摇伴随着船舶大角度横摇,不仅会降低船舶舒适性,而且当横摇角过大时还会造成集装箱的破坏与落水,带来经济损失。在不规则波中,船舶初稳性高是随波浪而随机变化,参数横摇呈现出非线性和随机性,因而增加了对这一问题的研究难度。采用数值模拟,从概率的角度探讨船舶在不规则随机纵浪中的参数横摇,用频率分布直方图分析不规则波中横摇角的频率分布,并分析横摇角概率分布受运动方程初值的影响。结果表明:不规则波中参数横摇的数值模拟结果会受运动方程初值的影响,不同的运动方程初值会导致不同的概率分析结果,可以选取合适的时间段,以减小初值的影响。
相似文献15.
本文用能量包线统计平均法研究船舶在随浪和斜浪作用下的横摇运动,适用于阻尼较小因而激励谱的带宽较之响应谐的带宽大得多的情况。通过解 FPK方程可得出能量包线的概率密度,进而计算出各种响应统计量。这一方法允许把激励谱的具体形式考虑进去,特别适用于有强非线性恢复力矩情况。 相似文献
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船舶在特定波浪环境下会遭遇大幅度的参数横摇运动。论文基于黏性流理论建立CFD数值模拟方法,结合动态重叠网格技术与刚体6自由度运动预报模块,对国际标准水面船模型ONRT,在横摇、纵摇与垂荡3自由度耦合运动情况下进行实尺度参数横摇数值模拟。还在安装不同附体(舭龙骨、呆木、尾舵)的条件下进行参数横摇数值预报。研究结果表明,加装舭龙骨对参数横摇具有显著的抑制作用,而呆木与尾舵虽然能在一定程度上减小参数横摇幅值,总体而言效果不显著。研究成果对船舶第二代完整稳性衡准的研究具有一定的参考意义。 相似文献
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《船舶与海洋工程学报》2021,(1)
A steady-state roll motion of ships with nonlinear damping and restoring moments for all times is modeled by a second-order nonlinear differential equation. Analytical expressions for the roll angle, velocity, acceleration, and damping and restoring moments are derived using a modified approach of homotopy perturbation method(HPM). Also, the operational matrix of derivatives of ultraspherical wavelets is used to obtain a numerical solution of the governing equation. Illustrative examples are provided to examine the applicability and accuracy of the proposed methods when compared with a highly accurate numerical scheme. 相似文献