ABSTRACT:

This study proposes a potential use of an oscillating water column (OWC) located inside a perforated caisson breakwater. Based on the linear potential theory, the interaction of water wave with the OWC is decomposed as a diffraction problem and a radiation problem as usual. This study only gives the analytical solution of the diffraction problem by means of the matched eigenfunction expansion method. Three parameters of engineering interest, the reflection coefficient, the vertical flux inside the OWC and the wave force acting on the whole structure, are examined. Some useful results are presented. The present study may provide an alternative low reflection OWC for engineers.

INTRODUCTION

Recently, various technologies of sea wave energy utilization have been extensively studied all over the world. A latest review on this topic has been given by Falcão (2010). The oscillating water column (OWC) is one of widely used wave power extraction devices. It generally includes a partially-immersed chamber with bottom open and with one or several Wells turbines. The incident wave induced oscillating motion of water surface inside the OWC can push the air through the Wells turbines, and then an electrical generator is driven by the turbines. In practice, the OWC devices are often installed on the coast or coastal structures rather than offshore, for reducing the costs of construction, maintenance, storage and so on. Especially, installing OWC devices on breakwaters seems to be a fine idea (e.g., Boccotti, 2007; Martins-Rivas and Mei, 2009). Perforated caisson breakwater is often used as a new type structure. It is initially proposed by Jarlan (1961) and consists of a perforated front wall, a solid rear wall and a wave absorbing chamber between the two walls. The advantages of perforated caissons are the lower reflection coefficient and smaller wave force (Li, 2007).

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