The hydrodynamic performance of an oscillating water column wave energy converter

A full description of the application of image shifting to the technique of particle image velocimetry (PIV) is given along with a discussion of the design and construction of a versatile rotating mirror image shifting system. The use of such a shifting system leads to systematic errors in the measured fluid velocities and it is shown that these errors can be accounted for and that a correction may be applied to eliminate them. A description of PIV itself and, in particular, the application of PIV to a study of the internal kinematics of an OWC in a wave flume is also provided. A simple semi-empirical model of the response of an OWC to a given wave climate is developed and its predictions are compared with air pressure and water level measurements obtained during flume tests of a model OWC. Finally detailed PIV time-series measurements, incorporating image shifting, are made of the flow within the OWC chamber and it is shown that as much as 7% of the wave energy may be lost due to viscous dissipation within the strong vortices which are formed around the submerged lip of the front wall of the model.