ABSTRACT

This paper presents an application of a three-dimensional numerical code for modelling Oscillating Water Column (OWC) devices extended from a conventional radiation-diffraction code - AQUADYN - developed for the study of floating bodies. The problem is formulated in the frequency domain for infinite or constant finite depth and it is based on classical linear water wave theory and potential flow. The extension of AQUADYN to OWC systems requires a modification in the dynamic boundary condition on the internal water free surface to account for the imposed oscillatory pressure distribution within the chamber.

INTRODUCTION

The research and development work on wave energy utilisation through wave power plants of the OWC type, has been based much on analytical models. In this field we can find basic studies performed by several authors, of which we point out the work described by Evans (1982), Malmo & Reitan (1985) and Evans & Porter (1995). A significant contribution to the hydrodynamic modelling of OWC devices consisted in the introduction of the spatial variation of the internal free surface of the OWC chamber, by Falcfio & Sarmento (1980), as opposite to the until then usual rigid piston approach. This theory was generalised by Evans (1982), and extended to a system composed of oscillating bodies and oscillating pressure distributions by Falnes & McIver, (1985). The mathematical modelling has been performed in mainly two-dimensions with simplified geometries, considering infinitely thin walls. As a result the final phases of plant design have been supported by laboratory tests with scale models. This experimental work has been mainly used to specify the appropriate design dimensions of the prototype (Ravindran et al, 1989, Joyce et al, 1993). Sarmento and Brito-Melo (1995) presented a 3D experimentalbased mathematical model of the Azores OWC Pico power plant.

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