Stability and Chaos Analysis of Nonlinear Roll Motion of Trimaran Ship With Variable Layouts Under Wind and Waves

2021 ◽  
Author(s):  
Zhang Yihan
Keyword(s):  
Roll Motion ◽  
Chaos Analysis ◽  
Nonlinear Roll Motion

Long-Term Extreme Response of a Vessel Rolling in Random Seas

2016 ◽  
Author(s):  
Wei Chai ◽  
Arvid Naess ◽  
Bernt J. Leira
Keyword(s):  
Nonlinear Effects ◽  
Roll Motion ◽  
Response Analysis ◽  
Linear Filter ◽  
Beam Seas ◽  
Random Seas ◽  
Extreme Response ◽  
High Level ◽  
Nonlinear Roll Motion

In this paper, the long-term extreme response of a vessel rolling in random beam seas is addressed. The long-term response analysis is based on the upcrossing rates of the roll motion under different sea states. However, the nonlinear effects associated with the restoring and damping terms have a significant influence on the high-level response, assessing the corresponding statistics, such as the upcrossing rate, with low probability levels is difficult and time-consuming. In this work, the Markov theory is introduced in order to tackle this problem. Specifically, the random roll excitation moment is approximated as a filtered white noise process by applying a linear filter technique and an efficient four-dimensional (4D) path integration (PI) procedure is applied in order to calculate the response statistics. The long-term analysis of nonlinear roll motion in random seas that takes into considerations of the response statistics obtained by the 4D PI method as well as the variation of the sea states could be a valuable reference for ship stability research.

scholarly journals NONLINEAR ROLLING STABILITY AND CHAOS RESEARCH OF TRIMARAN VESSEL WITH VARIABLE LAY-OUTS IN REGULAR AND IRREGULAR WAVES UNDER WIND LOAD

Brodogradnja ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 97-123
Author(s):  
Yihan Zhang ◽  
◽  
Ping Wang ◽  
Yachong Liu ◽  
Jingfeng Hu
Keyword(s):  
Heteroclinic Orbit ◽  
Melnikov Method ◽  
Wave Force ◽  
Nonlinear Damping ◽  
Wind Load ◽  
Irregular Waves ◽  
Roll Motion ◽  
Maximum Lyapunov Exponent ◽  
Moment Coefficient ◽  
Nonlinear Roll Motion

The trimaran vessel rolls strongly at low forward speed and may capsize in high sea conditions due to chaos and loss of stability, which is not usually considered in conventional limit-based criteria. In order to perfect the method of measuring roll performance of trimaran, a set of nonlinear roll motion stability analysis method based on Lyapunov and Melnikov theory was established. The nonlinear roll motion equation was constructed by CFD and high-order polynomial fitting method. The wave force threshold of rolling chaos in regular waves is calculated by Gauss-Legendre numerical integration method. The limited significant wave height of rolling chaos in random sea conditions is deduced by the phase space transfer rate, and the complex effect of wind load is superposed in the calculation. The influence of trimaran configuration on the roll system is analyzed through the state differentiation of homoclinic and heteroclinic orbit in phase portrait. The calculation of the maximum Lyapunov exponent further verified the applicability of Melnikov method, and the topological structure change of gradual failure of the rolling system is analyzed by the erosion of safe basin. The complex changes of the nonlinear damping coefficient and the nonlinear restoring moment coefficient caused by the change of the transverse lay-outs between the main hull and side hull have a significant influence on chaos and stability, and the existence of wind load has a certain weakening effect on the stability and symmetry of the system. The conclusion also further indicates the importance of the lay-outs to the dynamic stability of the trimaran vessel, which is significant for its seakeeping design.

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