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Mouvements de grande amplitude d'un corps flottant en fluide parfait. Application à la récupération de l'énergie des vagues.

Abstract : Wave energy converters (WECs) will be required to operate in severe seas. The Large amplitude of motions, and thus their numerical simulation can not be satisfactorily modelled by linear theory. So the primary goal of my research was to create a potentialmethod model for providing numerical simulations in time domain which can be used to assess various control strategies and hull shapes in different sea states. The first step has been to develop a 2D model to study the influence of the upper works of the SEAREV floating body. For this study, we chose to only take into account the Froude-Krylov forces on the instantaneous wetted surface. The incident wave field was given by the stream function theory of Rienecker & Fenton. The influence of the parts of upper works on the SEAREV device behavior has been realized by fixing the geometry of the hull whereas different shapes of the emerged part have been tested. A second step has been to create a linear 3D model to show how the production matrix of the SEAREV wave energy device is modified by the directional spreading of the wave spectrum and, to determine the resulting influence on the annual production at a given test site. In this approach, the computation of the hydrodynamic coefficients is performed by using the frequency-domain seakeeping computer code AQUADYN and the computation of the memory function by using the time-domain seakeeping code ACHIL3D. A cosine power '2s' function applied to a Pierson-Moskowitz spectrum is chosen to model the spreading. In the non-linear 3D model developed in a third stage, we have allowed the three-dimensional SEAREV device to be either floating on the free surface or completely immerged, and to undergo arbitrary six-degrees-of-freedom motions. The body motions have been described using three Cardan angles and the direct integration of the equations of motion implemented with a fourth order Runge-Kutta scheme. The fluid forces acting on the body can be non-linear with respect to certain motion variables, e.g. the quadratic component of Bernoulli's equation, the nonlinear incident potential flow. They contain “geometric” non-linearities as the forces are computed by integrating on the exact instantaneous position and wetted surface. The first-order force is calculated by a linear potential flow formulation whereas the second-order force is calculated by adding the quadratic term of Bernoulli's equation and by expanding the first-order force to the second-order using the Taylor expansion. The incident wave field is given by the stream function theory of Rienecker & Fenton as in the 2D model. Nonlinear irregular waves can also be generated by using a higher order spectral (HOS) formulation
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https://tel.archives-ouvertes.fr/tel-00521689
Contributor : Jean-Christophe Gilloteaux <>
Submitted on : Tuesday, September 28, 2010 - 1:26:04 PM
Last modification on : Thursday, January 11, 2018 - 6:17:20 AM
Long-term archiving on: : Wednesday, December 29, 2010 - 2:46:05 AM

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Jean-Christophe Gilloteaux. Mouvements de grande amplitude d'un corps flottant en fluide parfait. Application à la récupération de l'énergie des vagues.. Dynamique des Fluides [physics.flu-dyn]. Ecole Centrale de Nantes (ECN); Université de Nantes, 2007. Français. ⟨tel-00521689⟩

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