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Journal ArticleDOI

Wave generation by an oscillating surface-pressure and its application in wave-energy extraction

01 Jan 1985-Journal of Fluid Mechanics (Cambridge University Press)-Vol. 150, Iss: -1, pp 467-485
TL;DR: In this paper, a two-dimensional analysis based on linear surface-wave theory is developed for an oscillating-water-column wave-energy device in water of arbitrary constant depth, and the results show that air compressibility can be important in practice, and its effects may in general be satisfactorily represented by linearization.
Abstract: A two-dimensional analysis, based on linear surface-wave theory, is developed for an oscillating-water-column wave-energy device in water of arbitrary constant depth. The immersed part of the structure is assumed of shallow draught except for a submerged vertical reflecting wall. Both the cases of linear and nonlinear power take-off are considered. The results show that air compressibility can be important in practice, and its effects may in general be satisfactorily represented by linearization. The analysis indicates that using a turbine whose characteristic exhibits a phase difference between pressure and flow rate may be a method of strongly reducing the chamber length and turbine size with little change in the capability of energy extraction from regular waves. It was found in two examples of devices with strongly nonlinear power take-off that the maximum efficiency is only marginally inferior to what can be achieved in the linear case.
Citations
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Journal ArticleDOI
TL;DR: In this article, the development of wave energy utilization since the 1970s is discussed, with a focus on the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes.
Abstract: Sea wave energy is being increasingly regarded in many countries as a major and promising resource. The paper deals with the development of wave energy utilization since the 1970s. Several topics are addressed: the characterization of the wave energy resource; theoretical background, with especial relevance to hydrodynamics of wave energy absorption and control; how a large range of devices kept being proposed and studied, and how such devices can be organized into classes; the conception, design, model-testing, construction and deployment into real sea of prototypes; and the development of specific equipment (air and water turbines, high-pressure hydraulics, linear electrical generators) and mooring systems.

2,115 citations

Journal ArticleDOI
TL;DR: A comprehensive review of wave energy converters and air turbines can be found in this paper, together with a survey of theoretical, numerical and experimental modelling techniques of OWC converters.

594 citations


Cites methods from "Wave generation by an oscillating s..."

  • ...[149], based on a frequency-domain analysis of the hydrodynamics and a linearized isentropic assumption....

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Journal ArticleDOI
TL;DR: In this paper, a theoretical model is developed to simulate the energy conversion from wave to turbine shaft of an oscillating-water-column (OWC) plant equipped with a Wells air-turbine and with a valve (in series or in parallel with the turbine) for air-flow control.

258 citations

Journal ArticleDOI
TL;DR: In this article, a configuration of floating breakwater with asymmetric pneumatic chambers was proposed to increase the amplitude of the oscillating air-pressures inside both chambers over a wide range of wave frequency (thus to improve the performance in wave energy extraction).

197 citations

Journal ArticleDOI
TL;DR: In this paper, an oscillating water column (OWC) is studied experimentally to examine energy efficiencies for power take-off in a wave environment with plane progressive waves of steepness ranging from kA = 0.01 to 0.22 and water depth ratios varying from kh=0.30 to 3.72.
Abstract: An oscillating water column device enables the conversion of wave energy into electrical energy via wave interaction with a semi-submerged chamber coupled with a turbine for power take off. This present work concentrates on the wave interaction with the semi-submerged chamber, whereby a shore based oscillating water column (OWC) is studied experimentally to examine energy efficiencies for power take-off. The wave environment considered comprises plane progressive waves of steepnesses ranging from kA=0.01 to 0.22 and water depth ratios varying from kh=0.30 to 3.72, where k, A, and h denote the wave number, wave amplitude, and water depth, respectively. The key feature of this experimental campaign is a focus on the influence of front wall geometry on the OWC’s performance. More specifically, this focus includes: front wall draught, thickness, and aperture shape of the submerged front wall. We make use of a two-dimensional inviscid theory for an OWC for comparative purposes and to explain trends noted in the experimental measurements. The work undertaken here has revealed a broad banded efficiency centered about the natural frequency of the OWC. The magnitude and shape of the efficiency curves are influenced by the geometry of the front wall. Typical peak magnitude resonant efficiencies are in the order of 70%.

176 citations

References
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01 Jul 1958
TL;DR: In this paper, the evanescent field structure over the wave front, as represented by equiphase planes, is identified as one of the most important and easily recognizable forms of surface wave.
Abstract: This paper calls attention to some of the most important and easily recognizable forms of surface wave, pointing out that their essential common characteristic is the evanescent field structure over the wave front, as represented by equiphase planes. The problems of launching and supporting surface waves must, in general, be distinguished from one another and it does not necessarily follow that because a particular surface is capable of supporting a surface wave that a given aperture distribution of radiation, e.g. a vertical dipole, can excite such a wave. The paper concludes with a discussion of the behavior of surface waves and their applications.

1,244 citations

Journal ArticleDOI
TL;DR: In this article, the efficiency of energy absorption of a system of uniform oscillatory surface pressure distributions was derived based on linear water-wave theory and the results showed the close analogies which exist with theories for absorbing oscillatory rigid bodies and a number of new reciprocal relations for pressure distributions.
Abstract: Some general results are derived for the efficiency of energy absorption of a system of uniform oscillatory surface pressure distributions. The results, which are based on classical linear water-wave theory, show the close analogies which exist with theories for systems of absorbing oscillatory rigid bodies and a number of new reciprocal relations for pressure distributions are suggested and proved. Some simple examples illustrating the general results are given and compared with the corresponding results for rigid bodies.

356 citations

Journal ArticleDOI
TL;DR: In this article, the authors present an etude theorique du comportement thermodynamique de la turbine de Wells, a turbine a ecoulement axial adaptee a l'extraction d'energie a partir d'un energy alternatif, and obtention d'expressions for la forme d'ailette rendant maximal le rendement of the turbine.
Abstract: Presentation d'une etude theorique du comportement thermodynamique de la turbine de Wells, turbine a ecoulement axial adaptee a l'extraction d'energie a partir d'un ecoulement d'air alternatif. Developpement d'une analyse bidimensionnelle, et obtention d'expressions pour la forme d'ailette rendant maximal le rendement de la turbine. Analyse tridimensionnelle montrant que des distorsions radiales importantes du profil de vitesse axial peuvent se produire en fonction de la forme de l'ailette

61 citations

Book ChapterDOI
01 Jan 1973
TL;DR: In this paper, the authors discuss the problem of solving N real equations in N real unknowns, and present the best algorithms for the various facets of the given system, such as getting into a region of local convergence from poor initial estimates, achieving guaranteed convergence to a root from anywhere within a specified region by suitably restricting the functions fi, using a technique in a vicinity of a root (local technique) which is fast, stable and which does not require the user to furnish derivatives of the function fi; and finally, obtaining additional roots of a nonlinear system without converging again to
Abstract: Publisher Summary This chapter discusses the problem of solving N real equations in N real unknowns. It also presents the best algorithms for the various facets of the problem of solving the given system—getting into a region of local convergence from poor initial estimates; achieving guaranteed convergence to a root from anywhere within a specified region by suitably restricting the functions fi; using a technique in a vicinity of a root (local technique) which is fast, stable and which does not require the user to furnish derivatives of the functions fi; and finally, obtaining additional roots of a nonlinear system without converging again to previously found roots. The chapter mentions two approaches, namely, continuation by differentiation and heuristic search. Both these approaches bring systematically but slowly into a vicinity of a root in which one of the faster techniques is guaranteed to work.

40 citations