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The present study aims to evaluate the difference in the fluid-dynamic behavior of an overtopping wave energy converter under the incidence of irregular waves based on a realistic sea state when compared to the incidence of regular waves, representative of this sea state. Thus, the sea data of three regions from the Rio Grande do Sul coast, Brazil, were considered. Fluent software was employed for the computational modeling, which is based on the finite volume method (FVM). The numerical generation of waves occurred through the imposition of the velocity boundary conditions using transient discrete values through the WaveMIMO methodology. The volume of fluid (VOF) multiphase model was applied to treat the water–air interaction. The results for the water amount accumulated in the device reservoir showed that the fluid-dynamic behavior of the overtopping converter has significant differences when comparing the two proposed approaches. Differences up to 240% were found for the water mass accumulated in the overtopping device reservoir, showing evidence that the results can be overestimated when the overtopping device is analyzed under the incidence of the representative regular waves. Furthermore, for all studied cases, it was possible to approximate the water volume accumulated over time in the overtopping reservoir through a first-degree polynomial function.

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.

The present work proposes a numerical study of an overtopping wave energy converter. The goal of this study is to evaluate the theoretical power that can be converted by an overtopping device subjected to sea waves in the coastal region of Tramandaí, Brazil. For this, realistic irregular waves were generated using the WaveMIMO methodology, which allows numerical simulation of sea waves through the imposition of transient discrete data as prescribed velocity. For the numerical analysis, a two-dimensional computational model was employed using Fluent, where the device was inserted into a wave channel. The volume of the fluid multiphase model was used for the treatment of the air–water interaction. The results indicated that the free surface elevation obtained using the WaveMIMO methodology, which converts a realistic sea state into a free surface elevation series, was adequately represented. The evaluation of the theoretical power of the overtopping device during around 45 min indicated that 471.28 W was obtained. In addition, a monthly generation projection showed that this device would supply 100% of the electricity demand of a school in the city of Tramandaí. These results demonstrated that the conversion of sea wave energy into electrical energy can contribute to supplying electricity demand, especially for coastal cities.