Evaluation of the frequency dependent parameters and optimization of a floating OWC device

This thesis is focusing on the modeling of an offshore floating - moored OWC, because of the potential energy contained in waves far from the coast. The wave high distribution in Australia, mean during a year , is considering increasing with the distance from the coast. The mechanical oscillator model has been widely used to predict the movement of a shoreline fixed OWC (Folley and Whittaker, 2005) and a floating OWC (Stappenbelt and Cooper, 2009) . The use of this simple approach provides a first tuning tool, which is not completely considering every hydrodynamic aspect involved in the motion of the OWC and the chamber (that can be achieved using computational simulation of Navier – Stokes equation), but can predict the system behavior and the relative power output with a small computational load. This method allow the designer of the floating structure to tune the system using macro design parameter, in order to get the maximum efficiency from the energy converter device, for a known sea-state. This thesis is giving a method to get the parameters involved in the mechanical oscillator model and investigate how the natural frequencies of the structure and OWC are influencing the power output, in order to maximize it. The method consists in achieving these parameters by shaking the structure in still water in two different setups, include them in the dynamical model and verify that the predicted displacement and power production are comparable to the experimental results. Because of a good fitting of the experimental curves on the theoretical predictions it has been possible to develop some considerations about the design parameters of the device. A part of this thesis is also the linearization of the damping given by an orifice on top of the chamber, that is simulating the particular turbine used in the real model (Wells). This has been done using different filters, made by the present author.