Recovering the functional form of the nonlinear roll damping of ships from a free-roll decay experiment: An inverse formulism

Jang, Taichang; Kwon, Sun-Hong; Lee, J.H.

doi:10.1016/j.oceaneng.2010.06.012

Cited by 20 publications

(15 citation statements)

References 18 publications

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“…, Jang, et al (2010), Lee, et al (2012) 등은 감쇠실험을 부유체의 횡동요 연구 에 활용하였고, Chun, et al (2000a;2000b) 과 Kim, et al (2000) 등은 감쇠실험을 횡동요 저감장치의 성능파악에 활용하였다. …”

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Experimental Study of the Free Roll Decay Test for the Evaluation of Roll Damping Coefficients

Kim¹,

Kim²,

Ha³

2015

Journal of the Society of Naval Architects of Korea

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4This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.In general ships and FPSOs, roll damping is very small and consequently roll motion is very large at the roll resonance frequency. Proper evaluation of the roll damping coefficient at the resonance frequency is an important task in the study of roll motion and usually it is done by the analysis of free roll decay tests. The relative decrement method based on energy relation has been used mainly for the evaluation of roll damping coefficient from the roll decay test so far. As another method, the logarithmic decrement method based on equivalent linear decay assumption can be used for the same purpose and it is relatively simple. In this paper, both of the relative decrement method and the logarithmic decrement method are used for the evaluation of roll damping coefficient including quadratic damping from the free roll decay tests, and their results are cross-checked for verifying the obtained damping coefficients. Through applications to a box-type floating body equiped with bilge keels, it is shown that the two methods give almost the same damping coefficients in a practical view point and the cross-check of their results is to be a good tool to prevent a possible error. And also the quantitative effects of the bilge keels on the roll damping of box-type floating body are shown and discussed.

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Experimental Study of the Free Roll Decay Test for the Evaluation of Roll Damping Coefficients

Kim¹,

Kim²,

Ha³

2015

Journal of the Society of Naval Architects of Korea

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“…From the information of the measured response data for y and y  , the zerocrossing times of the displacement t i (i = 1,2,…) and the velocity t k (k = 1,2,…) and the stabilized u in eqn (10), it follows that the nonlinear damping at times t i is ( ) (19) and (20) for the two unknowns, f and r, respectively, have been reached.…”

Section: Simultaneous Identificationmentioning

confidence: 99%

“…However, most of this research has identified the nonlinear characteristics of either damping or the restoring force. Only in a few recent studies, there has been an attempt to identify the nonlinear characteristics of both [18,19].…”

Section: Introductionmentioning

confidence: 99%

A numerical scheme for recovering the nonlinear characteristics of a single degree of freedom structure: non-parametric system identification

Park¹,

Jang²,

Syngellakis³

et al. 2014

WIT Transactions on the Built Environment

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The aim of this paper is to present a numerical scheme for the identification of the nonlinear characteristics of a dynamically excited, single degree of freedom structure, using a non-parametric procedure, recently proposed by the second author; this involves the simultaneous identification of the nonlinear characteristics of both damping and restoring force in dynamic systems whose damping depends on velocity alone. According to this method, the response of the structure is first measured then an integral equation accounting for its unknown nonlinear characteristics is derived. This is an integral equation of the first kind, involving numerical instability in the Hadamard sense. To overcome this difficulty, the Landweber regularization, combined with the L-curve criterion, is applied to the integral equation. Adopting a dynamic model for a test structure, the corresponding nonlinear system identification is achieved through the proposed numerical solution of the governing integral equation.

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“…There are two approaches to achieve this: one is the parametric identification approach [5], and the other is the non-parametric identification approach [6]. In the parametric identification approach, one needs to presuppose the expressions of damping and stiffness, which are generally assumed to be odd-ordered polynomials, e.g., linear plus cubic damping…”

Section: Introductionmentioning

confidence: 99%

A Body-Nonlinear Green’s Function Method with Viscous Dissipation Effects for Large-Amplitude Roll of Floating Bodies

Guo

et al. 2018

Applied Sciences

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Abstract:A novel time-domain body-nonlinear Green's function method is developed for evaluating large-amplitude roll damping of two-dimensional floating bodies with consideration of viscous dissipation effects. In the method, the instantaneous wetted surface of floating bodies is accurately considered, and the viscous dissipation effects are taken into account based on the "fairly perfect fluid" model. As compared to the method based on the existing inviscid body-nonlinear Green's function, the newly proposed method can give a more accurate damping coefficient of floating bodies rolling on the free surface with large amplitudes according to the numerical tests and comparison with experimental data for a few cases related to ship hull sections with bilge keels.

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Recovering the functional form of the nonlinear roll damping of ships from a free-roll decay experiment: An inverse formulism

Cited by 20 publications

References 18 publications

Experimental Study of the Free Roll Decay Test for the Evaluation of Roll Damping Coefficients

Experimental Study of the Free Roll Decay Test for the Evaluation of Roll Damping Coefficients

A numerical scheme for recovering the nonlinear characteristics of a single degree of freedom structure: non-parametric system identification

A Body-Nonlinear Green’s Function Method with Viscous Dissipation Effects for Large-Amplitude Roll of Floating Bodies

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