This paper presents a methodology that allows the numerical simulation of realistic sea waves, called WaveMIMO methodology, which is based on the imposition of transient discrete data as prescribed velocity on a finite volume computational model developed in Fluent software. These transient data are obtained by using the spectral wave model TOMAWAC, where the wave spectrum is converted into a series of free surface elevations treated and processed as wave propagation velocities in the horizontal (x) and vertical (z) directions. The processed discrete transient data of wave propagation velocity are imposed as boundary conditions of a wave channel in Fluent, allowing the numerical simulation of irregular waves with realistic characteristics. From a case study that reproduces the sea state occurring on March 31st, 2014, in Ingleses Beach, in the city of Florianopolis, state of Santa Catarina, Brazil, it was concluded that the WaveMIMO methodology can properly reproduce realistic conditions of a sea state. In sequence, the proposed methodology was employed to numerically simulate the incidence of irregular realistic waves over an oscillating water column (OWC) wave energy converter (WEC). From these results, the WaveMIMO methodology has proved to be a promising technique to numerically analyze the fluid-dynamic behavior of WECs subjected to irregular waves of realistic sea state on any coastal region where the device can be installed.

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.

Spectral wave modelling is widely used to simulate large-scale wind–wave processes due to its low computation cost and relatively simpler formulation, in comparison to phase-resolving or hydrodynamic models. However, some applications require a time-domain representation of sea waves. This article proposes a methodology to transform the wave spectrum into a time series of water surface elevation for applications that require a time-domain representation of ocean waves. The proposed method uses a generated phase spectrum and the inverse Fourier transform to turn the wave spectrum into a time series of water surface elevation. The consistency of the methodology is then verified. The results show that it is capable of correctly transforming the wave spectrum, and the significant wave height of the resulting time series is within 5% of that of the input spectrum.

In this work, we conducted a numerical analysis of an oscillating water column (OWC) wave energy converter (WEC) device. The main objective of this research was to conduct a geometric evaluation of the device by defining an optimal configuration that maximized its available hydrodynamic power while employing realistic sea data. To achieve this objective, the WaveMIMO methodology was used. This is characterized by the conversion of realistic sea data into time series of the free surface elevation. These time series were processed and transformed into water velocity components, enabling transient velocity data to be used as boundary conditions for the generation of numerical irregular waves in the Fluent 2019 R2 software. Regular waves representative of the sea data were also generated in order to evaluate the hydrodynamic performance of the device in comparison to the realistic irregular waves. For the geometric analysis, the constructal design method was utilized. The hydropneumatic chamber volume and the total volume of the device were adopted as geometric constraints and remained constant. Three degrees of freedom (DOF) were used for this study: $H_1/L$ is the ratio between the height and length of the hydropneumatic chamber, whose values were varied, and $H_2/l$ (ratio between height and length of the turbine duct) and $H_3$ (submergence depth of hydropneumatic chamber) were kept constant. The best performance was observed for the device geometry with $H_1/L=$ 0.1985, which presented an available hydropneumatic power $P_{hyd}$ of 29.63 W. This value was 4.34 times higher than the power generated by the worst geometry performance, which was 6.83 W, obtained with an $H_1/L$ value of 2.2789, and 2.49 times higher than the power obtained by the device with the same dimensions as those from the one on Pico island, which was 11.89 W. When the optimal geometry was subjected to regular waves, a $P_{hyd}$ of 30.50 W was encountered.

The wave energy availability has become a field of intensive research around the world. In this sense, this study aims to estimate the wave climate at the most energetic spots on the South-Southeastern Brazilian Shelf (SSBS). To achieve this goal, the sea state model TOMAWAC was used to simulate 18 years of wave conditions on the SSBS. The results showed that the sites at Santa Marta cape and Ilhabela are quite similar, with mean wave height of 1.4 m and period of 8.5 s along the climatological year. Farol island, on the other hand, showed higher averages, of 1.7 m and 8.9 s for wave height and period, respectively. The annual behavior of the wave parameters showed greater stability at Santa Marta cape and Ilhabela, and less at Farol island. The mean wave power yield at the Santa Marta cape and Ilhabela is nearly 10 kW/m and at Farol island, 15 kW/m. A wavelet analysis pointed that the most energetic events are those with periods of occurrence from 6 to 12 days, with the apex at 7 days. The wavelet analysis also showed that the most energetic spectrum is the one at Farol island, with 2.5 times the energy of the other locations at the period band of 7 days.