Two-dimensional geometric optimization of an oscillating water column converter of real scale

Abstract

The present paper presents a two-dimensional numerical study about the geometric optimization of an ocean Wave Energy Converter (WEC) into electrical energy. The operational principle is based on the Oscillating Water Column (OWC). The main goal is to seek for the optimal geometry which maximizes the absorbed power take off (PTO) when it is subjected to a defined wave climate. To do so, Constructal Design is employed varying the degree of freedom (DOF) H1/L (ratio between the height and length of OWC chamber) and H3 (lip submergence), while the other DOF H2/l (ratio between height and length of chimney) is kept fixed. Moreover, the chamber and total areas of OWC device are also kept fixed, being the problem constraints. In this study was adopted a regular wave with real scale dimensions. For the numerical solution it is used the Computational Fluid Dynamic (CFD) commercial code FLUENT®, based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model is applied to tackle with the water-air interaction. The computational domain is represented by an OWC device coupled with the wave tank. The results led to a theoretical recommendation about the chamber geometry which maximizes the device performance, indicating that the higher efficiency (around 40 %) is obtained when H1/L = 0.13 and H3 = 9.50 m. On the other hand, the chamber geometry that generate the lower efficiency (around 4.4 %) is formed by H1/L = 0.03 and H3 = 9.00 m. One can note that the optimal shape is approximately 10 times more efficient than the worst geometry, showing the applicability and relevance of the Constructal Design method in the design of OWC-WEC.