A technology capable of converting the horizontal motion of the ocean waves into energy by the application of a flap-piston system has been improved over the last few years, this device is known as oscillating wave surge converter. This system has great potential, already proven, for electric power generation. The computational fluid dynamics is one of the most used tools for the study of wave energy converters. In this context, the present paper proposes the application of an alternative mesh morphing method to represent the hydrodynamics of these devices, which is based on a bottom that oscillates with the converter, leading the flap to reach high inclinations without causing numerical divergences. The study is performed using the OpenFOAM computational code and its extension OLAFOAM. These are based on Reynolds Average Navier Stokes (RANS) turbulence modeling and the Volume of Fluid method (VOF) for the free surface representation, which are applied to a bidimensional model, allowing the numerical modeling of the converter. The proposed method presented good agreement of the results when compared to the experimental studies in similar hydrodynamic cases. The methodology based on a moving bottom presented relative differences, concerning the method that considers the bottom as fixed, between 4% and 17% for the cases where the flap is near to the ocean bottom and up to 8% for cases where it is further away. RESUMOUma das tecnologias capazes de explorar a energia das ondas, baseada na captação das componentes horizontais do movimento destas, aliada a um sistema placa-pistão, vem experimentando um notável desenvolvimento ao longo dos últimos anos, tal dispositivo é conhecido como conversor oscilante por translação de ondas. Este possui um grande potencial, já comprovado, de geração de eletricidade. Uma das maneiras mais utilizadas para a análise destes conversores consiste na aplicação de ferramentas de modelagem numérica computacional. Neste contexto, o presente trabalho propõe a aplicação de uma metodologia numérica alternativa de deformação da malha de cálculo para representar a hidrodinâmica destes dispositivos, a qual está baseada em um fundo que oscila juntamente com o conversor, permitindo que este atinja inclinações elevadas, sem ocasionar divergências numéricas. O estudo é realizado pela aplicação do código computacional OpenFOAM, em conjunto com sua extensão OLAFOAM, que, através da metodologia Volume of Fluid (VOF), para a representação da superfície livre, e do método das médias de Reynolds (RANS), para a modelagem da turbulência, possibilita a simulação bidimensional da dinâmica do conversor considerado. O método proposto mostrou boa concordância e representatividade dos resultados, quando comparados a estudos experimentais, presentes na literatura, em situações hidrodinâmicas similares. Além disto, a metodologia baseada em um fundo móvel apresentou diferenças relativas, em relação ao método que considera o fundo como fixo, entre 4% e 17% para casos de placa muito próximos ao fundo do domínio e de até...

The Oscillating Wave Surge Converter represents a technology with great potential for generating electricity from ocean waves, promoting energy continuously throughout a day. Its development is on a pre-commercial scale and has been encouraging several companies and institutions to invest in the improvement and study of this conversion system. Simulations in Computational Fluid Dynamics are very important tools for the development of these converters, since they provide essential details for the analysis of the variables that influence the system. In this context, the present work uses the Large Eddy Simulation modeling to study the influence of the bottom slope on the device dynamics, which is performed using the OpenFOAM v.4.1 computational code and its extension OlaFlow. The model used in the analysis is two-dimensional and based on the Wall-Adapting Local Eddy-Viscosity methodology, while a structured mesh is applied. Through a detailed analysis, it was observed that the converter hydrodynamics is strongly influenced by the bottom slope, which is responsible for the intensification of the captured power in regions with slopes lower than 5º, and for the power decrease in cases where the slope exceeds 15º. Significant increases in slope can cause a decrease up to 28% in the converter excitation torque, significantly affecting its performance in electric power generation.

The Oscillating Wave Surge Converter (OWSC) is one of the most relevant systems for harnessing energy from ocean waves, generating energy by capturing the horizontal component of wave motion. This technology, which is on a pre-commercial development scale, presents one of the greatest potentials for electricity generation, due to its operating principle and the great improvement in design experienced over the last few years. Today, Computational numerical modelling is one of the main tools for the study and design of this and several other power generation systems from sea waves. In this context, a detailed study of a wave farm composed of several OWSCs is necessary, which represents a case closer to reality, since most renewable systems include several modules of the same converter. Considering the complexity of the existing hydrodynamics in these cases, a numerical modeling methodology based on the Large Eddy Simulation (LES) methodology is applied to correctly represent the oscillation of the structure and the observed flow fields. In order to achieve the objectives, the OpenFOAM v.4.1 computational code and the OlaFlow extension are used, together with the Wall Adapting Local Eddy Viscosity (WALE) LES model, which allows a representation of the system very close to real application cases. The proposed model demonstrated a good adherence of the results when compared to experimental studies present in the literature. Likewise, it was observed that changes in wave height and period, bottom slope, wave reflection, spacing between converters, and the wave farm layout can cause important variations in the energy generated by the system, increasing or reducing considerably its efficiency, emphasizing the importance of these parameters in the design and development of this technology.

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The Oscillating Wave Surge Converter (OWSC) is one of the most relevant systems for harnessing energy from ocean waves, generating energy by capturing the horizontal component of wave motion. This technology, which is on a pre-commercial development scale, presents one of the greatest potentials for electricity generation, due to its operating principle and the great improvement in design experienced over the last few years. Today, Computational numerical modelling is one of the main tools for the study and design of this and several other power generation systems from sea waves. In this context, a detailed study of a wave farm composed of several OWSCs is necessary, which represents a case closer to reality, since most renewable systems include several modules of the same converter. Considering the complexity of the existing hydrodynamics in these cases, a numerical modeling methodology based on the Large Eddy Simulation (LES) methodology is applied to correctly represent the oscillation of the structure and the observed flow fields. In order to achieve the objectives, the OpenFOAM v.4.1 computational code and the OlaFlow extension are used, together with the Wall Adapting Local Eddy Viscosity (WALE) LES model, which allows a representation of the system very close to real application cases. The proposed model demonstrated a good adherence of the results when compared to experimental studies present in the literature. Likewise, it was observed that changes in wave height and period, bottom slope, wave reflection, spacing between converters, and the wave farm layout can cause important variations in the energy generated by the system, increasing or reducing considerably its efficiency, emphasizing the importance of these parameters in the design and development of this technology.