Given the increasing global energy demand, the present study aimed to analyze the influence of bathymetry on the generation and propagation of realistic irregular waves and to geometrically optimize a wave energy converter (WEC) device of the oscillating water column (OWC) type. In essence, the OWC WEC can be defined as a partially submerged structure that is open to the sea below the free water surface (hydropneumatic chamber) and connected to a duct that is open to the atmosphere (in which the turbine is installed); its operational principle is based on the compression and decompression of air inside the hydropneumatic chamber due to incident waves, which causes an alternating air flow that drives the turbine and enables electricity generation. The computational fluid dynamics software package Fluent was used to numerically reproduce the OWC WEC according to its operational principles, with a simplification that allowed its available power to be determined, i.e., without considering the turbine. The volume of fluid (VOF) multiphase model was employed to treat the interface between the phases. The WaveMIMO methodology was used to generate realistic irregular waves mimicking those that occur on the coast of Tramandaí, Rio Grande do Sul, Brazil. The constructal design method, along with an exhaustive search technique, was employed. The degree of freedom $H_1/L$ (the ratio between the height and length of the hydropneumatic chamber of the OWC) was varied to maximize the available power in the device. The results showed that realistic irregular waves were adequately generated within both wave channels, with and without bathymetry, and that wave propagation in both computational domains was not significantly influenced by the wave channel bathymetry. Regarding the geometric evaluation, the optimal geometry found, ${\left(H_1/L\right)}_o$ = 0.1985, which maximized the available hydropneumatic power, i.e., the one that yielded a power of 25.44 W, was 2.28 times more efficient than the worst case found, which had $H_1/L$ = 2.2789.

Aiming to contribute to studies related to the generation of electrical energy from renewable sources, this study carried out a geometric investigation of an oscillating water column (OWC) wave energy converter (WEC) device. The structure of this device consists of a hydropneumatic chamber and an air duct, where a turbine is coupled to an electrical energy generator. When waves hit the device, the air inside it is pressurized and depressurized, causing the air to flow through the duct, activating the turbine. In this sense, the present study used the constructal design method to evaluate the influence of the ratio between the height and length of the hydropneumatic chamber ($H_1/L$) on the mean available hydropneumatic power ($P_{H\left(\mathrm{R}\mathrm{M}\mathrm{S}\right)}$). Fluent software was used to perform numerical simulations of representative regular waves from the sea state in the municipality of Tramandaí, southern Brazil, impacting the OWC. Thus, it was possible to identify the geometry that maximized the performance of the OWC WEC, with ${(H_1/L)}_O=0.3430$, yielding $P_{H\left(\mathrm{R}\mathrm{M}\mathrm{S}\right)}=56.66$ W. In contrast, the worst geometry was obtained with $H_1/L=0.1985$, where $P_{H\left(\mathrm{R}\mathrm{M}\mathrm{S}\right)}=28.19$ W. Therefore, the best case is 101% more efficient than the worst one.

Among the various potential renewable energy sources, sea waves offer significant potential, which can be harnessed using wave energy converter (WEC) devices such as overtopping converters. These devices operate by directing incident waves up a ramp into a reservoir. The water then passes through a turbine coupled with an electrical generator before returning to the ocean. Thus, the present study deals with the geometrical evaluation of an overtopping WEC, where the influence of the ratio between the height and length of the device ramp ($H_1/L_1$) on the amount of water mass (M) that enters the reservoir was investigated. Numerical simulations were performed using ANSYS-Fluent software, 22 R1 version, to generate and propagate realistic irregular (RI) waves and representative regular (RR) waves found in the coastal region of the municipality of Rio Grande, in the state of Rio Grande do Sul, southern Brazil. Consequently, through constructal design, the optimal WEC geometry for both wave approaches were identified as the same, where (${H_1/L_1)}_o=0.30$. Thus, considering the RI waves, $M=$ 200,820.77 kg was obtained, while, considering the RR waves, $M=$ 144,054.72 kg was obtained.

Irregular wave generation in numerical simulations is critical for accurately modeling realistic sea conditions, which is essential in coastal and offshore engineering applications, such as for wave energy conversion. Therefore, this study presents theoretical recommendations for generating realistic irregular waves using the WaveMIMO methodology and validates its accuracy against experimental data. For the parameters investigation, spectral data are processed to obtain orbital velocity profiles of wave propagation, which are imposed as boundary conditions (BCs) in a numerical wave channel. The simulations were conducted using the ANSYS-Fluent 2024 R2 software, which employs the multiphase volume of fluid (VOF) model to treat the interface between phases. Seeking theoretical recommendations for the application of this methodology, the present study investigated the discretization of the region where the prescribed velocity BC is imposed, the mesh sensitivity in the free surface region, the time step used, and the location of the velocity vector in each segment of the prescribed velocity BC imposition region. The results obtained were compared with realistic sea state data obtained from the TOMAWAC spectral model, referring to the municipalities of Rio Grande and Tramandaí, in the state of Rio Grande do Sul, Brazil. The results indicated that, compared to recommendations from the previous literature, the recommended configuration improved wave generation accuracy by 7–8% for Rio Grande and 2–3% for Tramandaí. Finally, the WaveMIMO methodology and its theorical recommendations were validated against experimental data found in the literature, reaching an excellent agreement.

Dentre as diversas fontes renováveis de energia que podem ser exploradas, têm-se a energia contida nas ondas do mar. A metodologia WaveMIMO é utilizada para a geração numérica de ondas irregulares baseadas em estados de mar realísticos e consiste em tratar dados espectrais para a obtenção de perfis de velocidade orbital de propagação das ondas, que são impostos como condição de contorno (CC) em um canal de ondas numérico. Nesse sentido, o presente estudo avalia parâmetros para a aplicação desta metodologia, onde se investigou a discretização da região de imposição da CC de velocidade prescrita, a sensibilidade de malha na região da superfície livre, o passo de tempo empregado e, por fim, a localização do vetor de velocidades em cada segmento da região de imposição da CC de velocidade prescrita. Para tanto, foram considerados dados realísticos referentes a um ponto próximo à costa do município de Mostardas, no estado do Rio Grande do Sul, obtidos do modelo espectral TOMAWAC. Os resultados indicaram que, comparando o melhor e o pior caso avaliado, obteve-se melhorias de 6,58% e 7,60% nas métricas consideradas nas avaliações dos resultados.