Mateus das Neves Gomes

Numerical Study of the Effect of the Relative Depth on the Overtopping Wave Energy Converters According to Constructal Design

The conversion of wave energy in electrical one has been increasingly studied. One example of wave energy converter (WEC) is the overtopping device. Its main operational principle consists of a ramp which guides the incoming waves into a reservoir raised slightly above the sea level. The accumulated water in the reservoir flows through a low head turbine generating electricity. In this sense, it is performed a numerical study concerned with the geometric optimization of an overtopping WEC for various relative depths: d/λ = 0.3, 0.5 and 0.62, by means of Constructal Design. The main purpose is to evaluate the effect of the relative depth on the design of the ramp geometry (ratio between the ramp height and its length: H1/L1) as well as, investigate the shape which leads to the highest amount of water that insides the reservoir. In the present simulations, the conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the finite volume method (FVM). To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. Results showed that the optimal shape, (H1/L1)o, has a strong dependence of the relative depth, i.e., there is no universal shape that leads to the best performance of an overtopping device for several wave conditions.

Numerical analysis including pressure drop in oscillating water column device

Abstract The wave energy conversion into electricity has been increasingly studied in the last years. There are several proposed converters. Among them, the oscillatingwater column (OWC) device has been widespread evaluated in literature. In this context, the main goal of this work was to perform a comparison between two kinds of physical constraints in the chimney of the OWC device, aiming to represent numerically the pressure drop imposed by the turbine on the air flow inside the OWC. To do so, the conservation equations of mass,momentumand one equation for the transport of volumetric fraction were solved with the finite volume method (FVM). To tackle thewater-air interaction, the multiphase model volume of fluid (VOF)was used. Initially, an asymmetric constraint inserted in chimney duct was reproduced and investigated. Subsequently, a second strategywas proposed,where a symmetric physical constraint with an elliptical shapewas analyzed. Itwas thus possible to establish a strategy to reproduce the pressure drop in OWC devices caused by the presence of the turbine, as well as to generate its characteristic curve.

Numerical Approach of the Main Physical Operational Principle of Several Wave Energy Converters: Oscillating Water Column, Overtopping and Submerged Plate

In this work it is numerically studied the wave flow inside a tank and the main operational physical principle of three different wave energy converters (WEC): oscillating water column (OWC), overtopping and submerged plate. The wave energy converters are evaluated in laboratory and real scales. For all studied cases the conservation equations of mass, momentum and one equation for the transport of volumetric fraction are solved with the finite volume method (FVM). To tackle with water-air mixture, the multiphase model Volume of Fluid (VOF) is used. Several results showed the accuracy of the numerical approach for estimation of the physical phenomenon of wave flow inside tanks, as well as, its interaction with the studied devices. For the cases with geometrical optimization, Constructal Design is employed for geometrical evaluation of the devices. Results presented several theoretical recommendations about the influence of geometrical parameters (such as ratios between heights and lengths of OWC chamber and ramp of overtopping device and the distance from the plate to the seabed of wave tank) over the available power take off (PTO) in the OWC and submerged plate devices and over the amount of water stored in the reservoir of the overtopping device. Results showed the importance of geometric shapes over the devices performance. Moreover, it is evaluated the influence of several wave parameters (such as wave period and relative depths) over the fluid dynamic performance of the devices and geometrical parameters of the devices. It is noticed the non-occurrence of universal optimal shapes.

Energy from the Sea: Computational Modeling of an Overtopping Device

This work presents a brief study about the wave energy as well as a computational modeling of an overtopping device. The numerical simulation was performed with the FLUENT® Computational Fluid Dynamic software code, employing the multiphase Volume of Fluid (VOF) model. The obtained results showed a satisfactory agreement between the numerical and analytical solutions, being the maximum difference calculated for the wave generation of approximated 4.6%. It was also observed that the knowledge of the wave height and an adequate ramp design are factors that determine the overtopping occurrence.

Computational Modeling of an Oscillating Water Column Device for the Rio Grande Coast

This work presents the computational modeling of a converter of wave energy in electrical energy. The converter is Oscillating Water Column (OWC) type, submitted to the wave climate of Rio Grande city. The numerical simulation was performed using FLUENT® package and employing the multiphase Volume of Fluid (VOF) model in the wave generation and in the interaction between the wave and the converter device. The computational domain was represented by a wave tank coupled with the OWC device. This domain allows the behavior analysis to be performed when the device is subjected to the incidence of regular waves. The waves were molded to represent the characteristics of the Rio Grande coast climate. Results demonstrate that the OWC converter can be successfully used to convert the Rio Grandes coast wave energy in useful electrical energy.

ANÁLISE NUMÉRICA DA GEOMETRIA DA RAMPA DE UM DISPOSITIVO DE GALGAMENTO ONSHORE EM ESCALA REAL APLICANDO O DESIGN CONSTRUTAL

O presente trabalho propoe um estudo numerico a respeito de um conversor de energia das ondas do mar do tipo galgamento. O principio operacional do dispositivo de galgamento consiste de uma estrutura que utiliza uma rampa para direcionar as ondas incidentes para o reservatorio. A agua armazenada retorna ao oceano apos a passagem por uma turbina que esta acoplada a um gerador de energia eletrica. O objetivo deste estudo e a aplicacao do metodo Design Construtal, aliado a busca exaustiva, na definicao da melhor forma geometrica para a rampa de modo a maximizar a vazao massica de agua que entra no reservatorio. O grau de liberdade b/B foi otimizado. A restricao considerada neste estudo e manter fixo: a area total do tanque de ondas, a area da rampa e as caracteristicas da onda. Para a analise numerica do principio de funcionamento deste dispositivo foi empregado um dominio computacional tridimensional (3D), construido e discretizado no software GAMBIT, onde o conversor e acoplado a um tanque de ondas regulares. As solucoes das equacoes de conservacao e uma equacao para o transporte da fracao volumetrica foram realizadas com o codigo comercial de Dinâmica dos Fluidos Computacional FLUENT, que e baseado no Metodo de Volumes Finitos (MVF). Aplica-se o modelo multifasico Volume of Fluid (VOF) no tratamento da interacao agua-ar. Os resultados conduziram a uma recomendacao teorica sobre a geometria otima do dispositivo de galgamento, mostrando que houve uma razao otima (b/B) o = 0.38, que maximiza a quantidade de agua que entra no reservatorio. Palavras-chave: Galgamento, Teoria Construtal, Analise Numerica.

Numerical Analysis of the Oscillating Water Column (OWC) Wave Energy Converter (WEC) Considering Different Incident Wave Height

The ocean wave energy conversion into electricity has been increasingly researched in the last years. There are several proposed converters, among them the Oscillating Water Column (OWC) device has been widely studied. The present paper presents a two-dimensional numerical investigation about the fluid dynamics behavior of an OWC Wave Energy Converter (WEC) into electrical energy. The main goal of this work was to numerically analyze the optimized geometric shape obtained in previous work under incident waves with different heights. To do so, the OWC geometric shape was kept constant while the incident wave height was varied. For the numerical solution it was used the Computational Fluid Dynamic (CFD) commercial code FLUENT®, based on the Finite Volume Method (FVM). The multiphasic Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The computational domain is represented by the OWC device coupled with the wave tank. This work allowed to check the influence of the incident wave height on the hydropneumatic power and the amplification factor of the OWC converter. It was possible to identify that the amplification factor increases as the wave period increases, thereby improving the OWC performance. It is worth to highlight that in the real phenomenon the incident waves on the OWC device have periods, lengths and height variables.