Numerical analysis of a water column and structure heave velocity relationship for a floating oscillating water column wave energy device
This paper investigates a method to determine the relative power production potential of a floating oscillating water column wave energy converter. This method focuses on determining the key characteristics of the parametric function relating the water column heave velocity to the structure heave velocity. The numerical investigation is undertaken using single frequency sinusoidal waves using WAMIT and OrcaFlex. The paired velocities of the structure and the water column surface follow an elliptical function. The properties of this ellipse yields interesting information about the power produced by the OWC. It has been determined through investigation into the length and gradient of the major (long) and minor (short) axes of the bisector of the ellipse that relates the vertical water column heave velocity to the structure heave velocity that the power production potential is linearly proportional to the magnitude of of relative velocity between the water column and floating structure more so than a phase difference between these two velocities. It has also been determined that the lengths of both axes of the ellipse are maximised, and hence system efficiency, when the forcing frequency is equal to approximately 90-100% of the of natural frequency of the water column of the system in question.