SVR-based identification of nonlinear roll motion equation for FPSOs in regular waves

2015 ◽  
Vol 109 ◽  
pp. 531-538 ◽  
Author(s):  
Xian-Rui Hou ◽  
Zao-Jian Zou
Keyword(s):  
Motion Equation ◽  
Roll Motion ◽  
Regular Waves ◽  
Nonlinear Roll Motion

Force Analysis of the Anchor Chains and the Cable in the Crane-System with a Floating Base in Regular Waves

2014 ◽  
Vol 494-495 ◽  
pp. 321-327
Author(s):  
Ya Xin Huang ◽  
Bing Wang ◽  
Jun Yi Liu
Keyword(s):  
Numerical Simulation ◽  
Discrete Time ◽  
Time History ◽  
Roll Motion ◽  
Force Analysis ◽  
Time Transfer ◽  
Regular Waves ◽  
Body Model ◽  
Floating Base ◽  
Rigid Body Model

In order to analyze the force of the anchor chains and the cable in the crane-system with a floating base, firstly the system is simplified to two-rigid-body model and the anchor chains in the system are in symmetric layout; then the motion response of the system as well as the force of the anchor chains and the cable are solved by use of discrete time transfer matrix method, lastly the time history curves of motion of the system and the force of the anchor chains and the cable are obtained. The results of numerical simulation show that the roll motion has greater influences on the system comparing with sway and heave, the amplitudes of sway and heave are small. Furthermore, the force of the anchor chains are mainly caused by the roll motion while the force caused by sway and heave are relatively small.

Experimental Study of Sloshing Effects in Roll Motion of Floating Units

2008 ◽  
Author(s):  
Higor Felipe de Medeiros ◽  
Guilherme Espan˜a Rueda Silva ◽  
Liang-Yee Cheng ◽  
Marcio Michiharu Tsukamoto ◽  
Kazuo Nishimoto
Keyword(s):  
Traditional Approach ◽  
Ship Motion ◽  
Roll Motion ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Regular Waves ◽  
Coupling Effects ◽  
Bibliographical Survey ◽  
Sea Wave ◽  
Numerical Approaches

Usually, the hydrodynamic loads due to sloshing are considered in the design of liquid cargo ship or floating units concerning the structural. Owing to the increasing size of these structures, resonant sloshing motions may occur and result in the amplification or attenuation of motion of the vessel. In order to assess the effect of sloshing, traditionally the motion of the vessel is calculated at first without considering the dynamic of the liquid inside the tank. After that, this motion of the vessel is inputted as excitation motion acting on the tank and, finally, the sloshing effect is evaluated. In the other words, the coupling effects of sloshing and sea wave in the vessel’s motion are ignored. A bibliographical survey shows that there are few studies that consider the effect of sloshing on the ship motion, acting as a passive device of absorption of the movements. The main goal of this research is to investigate experimentally the roll motion amplification and reduction due to sloshing. The coupling effects of sloshing and sea wave in the vessel’s motion are taking into account by recording the motions, in regular waves, of a free floating model with a partially filled liquid tank. For this purpose, a two-dimensional model is designed to carry out measurements with fixed cargo and partially filled liquid cargo. The experimental results are evaluated by comparing the measured motion of the free-floating model with fixed cargo against the results obtained by traditional approach. Then, the effects of sloshing on floating units are shown by comparison of the measurements from free-floating model with fixed cargo and liquid cargo. The results shown herein provide data for the validation of new numerical approaches for the study of the coupled motions of the floating units and sloshing.

Numerical Analysis of Added Resistance on Ship in Parametric Roll Motions

2016 ◽  
Author(s):  
Jae-Hoon Lee ◽  
Yonghwan Kim ◽  
Min-Guk Seo
Keyword(s):  
Near Field ◽  
Three Dimensional ◽  
Field Method ◽  
Roll Motion ◽  
Added Resistance ◽  
Regular Waves ◽  
Nonlinear Formulation ◽  
Parametric Roll ◽  
Weakly Nonlinear ◽  
Rankine Panel Method

In the present study, the added resistance of a containership in parametric roll motion is investigated. The numerical simulation is carried out using a three dimensional Rankine panel method along with the weakly nonlinear formulation. The added resistance is evaluated by a near-field method, namely, the direct integration of the 2nd-order pressure on a body surface. To calculate the component resulting from the large-amplitude roll motion, the higher-order restoring and Froude-Krylov forces on wetted hull surfaces are taken into account. With or without parametric roll in regular waves, the components of added resistance classified with respect to integral terms are compared to figure out the important of each term. Through the investigation, the correlation between the added resistance and parametric roll is derived from coupling and decoupling the components of roll motion and vertical motions.

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.

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