INTERNATIONAL JOURNAL OF HEAT AND TECHNOLOGY Vol.33, No.2, 2015 http://dx.doi.org/10.18280/ijht.330205 1. INTRODUCTION The renewable energy technologies are a crucial part of a portfolio of options that are required to achieve a secure and sustainable energy mix in a country. Among the benefits that renewable energy can provide are less environmental impact, including emissions of greenhouse gases and local pollutants; energy security; strategic and economic development, including rural development, agriculture and high-tech production [1]. The most studied sources of renewable energy are solar, wind, geothermal, biomass, and ocean. Ocean energy is an inexhaustible source with an estimated theoretical potential greater than 100,000 TWh/year (as a reference, the consumption of electricity in the world is about 16,000 TWh/year) [2]. Ocean energy types can be classified by its origin. Mainly there are ocean tidal energy generated by the interaction of gravitational fields of sun and moon, ocean thermal energy which is due to solar radiation, ocean currents energy caused by gradients of temperature, salinity and tidal action, and wave energy as a result of wind action [3]. The wave energy converters (WECs) can be classified with the principle of energy transformation. The three most common devices are: Oscillating Water Column (OWC), Wave Activated Bodies (WAB) and Overtopping Devices (OTD). The aim of the present study is to carry out a numerical study to optimize the geometry and submergence of the OWC device subjected to regular waves with real conditions. The optimization was done using Constructal Design (which is based in Constructal Theory) developed by Adrian Bejan [4- 7]. Constructal Theory has been used in previous works involving WECs. In [8] and [9] Constructal Design was used for the geometric optimization of an OWC, varying the CONSTRUCTAL DESIGN APPLIED TO THE STUDY OF THE GEOMETRY AND SUBMERGENCE OF AN OSCILLATING WATER COLUMN Giulio Lorenzini*, Maria Fernanda Espinel Lara°, Luiz Alberto Oliveira Rocha*, Mateus das Neves Gomes + , Elizaldo Domingues dos Santos # , Liércio André Isoldi § * Dipartimento di Ingegneria Industriale, Università degli Studi di Parma, Parco Area delle Scienze 181/A, 43124 Parma, Italy, giulio.lorenzini@unipr.it, corresponding; °,* Departamento de Engenharia Mecânica, Universidade Federal do Rio Grande do Sul, Rua Sarmento Leite, 425, Porto Alegre, RS, 90.050-170, Brazil, maria.lara@ufrgs.br, luizrocha@mecanica.ufrgs.br; + Instituto Federal do Paraná, Campus Paranaguá, Rua Antônio Carlos Rodrigues 453, bairro Porto Seguro, Paranaguá, PR, 83215-750, Brazil, mateus.gomes@ifpr.br; #, § School of Engineering, Universidade Federal do Rio Grande, Av. Itália Km 8, bairro Carreiros, Rio Grande, RS, 96201-900, Brazil, elizaldosantos@furg.br, liercioisoldi@furg.br. ABSTRACT The wave energy conversion into electricity has been increasingly studied in the last years. There are several converters, among them the Oscillating Water Column (OWC) device. Constructal Design and a computational modeling were applied to a geometric optimization of an Oscillating Water Column Wave Energy Converter, device that transforms the energy of incident waves into electrical energy. The aim is to convert maximum electrical power varying and analyzing the influence of the three degrees of freedom (DoFs): H1/L (ratio between the height and length of OWC chamber), H2/l (ratio between height and length of chimney), and H3 (submergence, which are related to the chamber and the chimney of the device, and the location in water depth respectively. Besides there are two constraints (fixed parameters): total area of the OWC chamber (A1) and total area of OWC device (A2). The computational domain consists of an OWC inserted in a tank where regular waves in a real scale are generated. The mesh was developed in ANSYS ICEM ® . The computational fluid dynamics code ANSYS FLUENT ® was used to find the numerical solution which is based on Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The results led to a theoretical recommendation about the OWC geometry and its submergence which maximizes the device performance, since a redistribution of the OWC geometry and a variation in the value of its submergence could improve the hydropneumatic power from 10.7 W to 190.8 W for ratios H1/L, H2/l and H3 equal 0.135, 6.0 and 9.5 m respectively, and incident waves characterized by a period of 5 s and wave length of 37.6 m. Keywords: Wave Energy Converter, Oscillating Water Column, Constructal Design, Numerical wave tank. 31