Asymmetric roll center of symmetric body in beam waves

Fernandes, Antonio Carlos; Asgari, Peyman; Soares, Anderson

doi:10.1016/j.oceaneng.2015.12.001

Cited by 13 publications

(4 citation statements)

References 1 publication

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“…As a result, The water depth could be controlled and in the present experiments was set to 0.5 m. Uniform main flow was produced by four centrifugal water pumps. The maximum achievable current velocity in the channel was 0.5 m/s [32]. Its correspondent Hydraulic Froude number (Frh ¼ V= ffiffiffiffiffiffi ffi gH p ) was 0.22.…”

Section: Model Setupmentioning

confidence: 99%

From fluttering to autorotation bifurcation of a flat plate in a current

Rostami

Fernandes

2017

J Braz. Soc. Mech. Sci. Eng.

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This paper is dedicated to both the simulation of fluttering (oscillatory) and autorotation of a vertically hinged flat plate that may occur under the action of a fluid current and the experiments of the same vertical flat plate. Fluttering is defined as the oscillation of a body around an axis, whereas autorotation is a continuous rotational mode around the same axis. Both mentioned rotational motions occur without external power, and they are excited by the incident current. This paper describes the simulation of these phenomena by a nonlinear time domain code. The paper also considers the effect of mass moment of inertia on vortex shedding frequency and the resultant dynamics. The main inertia parameter (I*) is defined as the ratio between the mass moment of inertia and the added moment of inertia. It is shown that by increasing I*, fluttering bifurcates to autorotation at I* = 0.162, being the transition approximately independent of the current velocity, or of the corresponding Reynolds number. The results show that Strouhal number drops when fluttering translates to autorotation. Moreover, a method is proposed to calculate the theoretical extractable power from fluttering and autorotation using a phase diagram of angular acceleration versus velocity.

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Section: Model Setupmentioning

confidence: 99%

From fluttering to autorotation bifurcation of a flat plate in a current

Rostami

Fernandes

2017

J Braz. Soc. Mech. Sci. Eng.

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“…The authors obtained the ICR by intersecting the perpendiculars to the velocity vectors measured at two distinct points in the floating body: this approach is, in fact, well established in the general kinematics theory [13], and will form the basis for the current investigation, as explained in Section 2. Fernandes et al [14] built on that study by performing experiments in regular waves close to the roll natural period, supported by additional numerical calculations in the frequency domain. The authors showed that the ICR locus of an FPSO vessel is a straight line not coinciding with the line of symmetry of the vessel, dependent on the frequency of the waves.…”

Section: Previous Workmentioning

confidence: 96%

“…Identification of such point is crucial as it can improve the understanding of the dynamic behaviour of FOWT, which, in turn, can lead to better motion reduction methods and may be leveraged to improve the design of these highly dynamic systems. 1 Since the CR does not necessarily coincide with the centroid of the waterplane area [14] (except for the special case of very small rotations with no dynamic forces acting on the freely floating body), the side of the floater facing the incoming waves experiences different 1 Note that identification of ICR is not strictly required to compute the responses with fully-coupled aero-hydro-servo-elastic nonlinear time domain dynamic solvers, in which case the physics of the problem (distributed loads) drive the ICR, and not vice versa. The knowledge of ICR is useful for lowerfidelity numerical models that make assumptions about the centre of rotation (CR), as well as to understand the FOWT coupled motion patterns.…”

Section: Motivationmentioning

confidence: 99%

Rigid Body Dynamic Response of a Floating Offshore Wind Turbine to Waves: Identification of the Instantaneous Centre of Rotation Through Analytical And Numerical Analyses

Patryniak

Collu

Coraddu

2023

Preprint

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“…In this method a fixed center of rotation must be assumed. Assuming it even exists, determining an approximate center of rotation is a difficult task (see for instance [3]). Since the vessel is free to roll and sway, center of rotation is a less problematic issue in free decay tests.…”

Section: Introductionmentioning

confidence: 99%

Bilge Keel Induced Roll Damping of an FPSO With Sponsons

Ommani

Fonseca

Kristiansen

et al. 2016

Volume 1: Offshore Technology; Offshore Geotechnics

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The bilge keel induced roll damping of an FPSO with sponsons is investigated numerically and experimentally. The influence of the bilge keel size, on the roll damping is studied. Free decay tests of a three-dimensional ship model, for three different bilge keel sizes are used to determine roll damping coefficients. The dependency of the quadratic roll damping coefficient to the bilge keel height and the vertical location of the rotation center is studied using CFD. A Navier-Stokes solver based on the Finite Volume Method is adopted for solving the laminar flow of incompressible water around a section of the FPSO undergoing forced roll oscillations in two-dimensions. The free-surface condition is linearized by neglecting the nonlinear free-surface terms and the influence of viscous stresses in the free surface zone, while the body-boundary condition is exact. An averaged center of rotation is estimated by comparing the results of the numerical calculations and the free decay tests. The obtained two-dimensional damping coefficients are extrapolated to 3D by use of strip theory argumentations and compared with the experimental results. It is shown that this simplified approach can be used for evaluating the bilge keel induced roll damping with efficiency, considering unconventional ship shapes and free-surface proximity effects.

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Asymmetric roll center of symmetric body in beam waves

Cited by 13 publications

References 1 publication

From fluttering to autorotation bifurcation of a flat plate in a current

From fluttering to autorotation bifurcation of a flat plate in a current

Rigid Body Dynamic Response of a Floating Offshore Wind Turbine to Waves: Identification of the Instantaneous Centre of Rotation Through Analytical And Numerical Analyses

Bilge Keel Induced Roll Damping of an FPSO With Sponsons

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