Jaifer Corrêa Martins

The present work investigates the influence of rectangular deflectors on the performance of a Savonius turbine mounted in an L-shaped channel, which represents a geometry like that found in one oscillating water column (OWC) device. It also performs a geometric investigation of the entrance region of the channel. More precisely, it investigates the effect of the height/length ratio (H₁/L₁) of the entering region of the channel on the system performance for three different configurations: (1) without the use of deflectors, (2) with just one deflector upstream the turbine, and (3) with one deflector upstream and another downstream the turbine. The geometric investigation is performed based on the constructal design method, and the entering channel area (A₁) is the problem constraint. The performance indicators are the mechanical power in the Savonius turbine and the available power in the device. For all cases, it is considered turbulent airflow in the domain, being solved by the unsteady Reynolds Averaged Navier–Stokes mass and momentum equations. The numerical solution was obtained with the finite-volume method using the Ansys FLUENT software (version 2021 R1). The k-ω shear stress transport turbulence closure model is used. The results demonstrated that the mechanical and available powers depend on the H₁/L₁ ratio, regardless of the usage of deflectors. For instance, differences of up to 16.35% in mechanical power and 7.25% in available power were observed between the best and worst performance configurations in the case without deflectors. The use of deflectors resulted in increases of two and three times in available and mechanical powers, respectively, when the cases with one and two deflectors are compared with those without deflectors. This demonstrates that the enclosed domain and the insertion of the deflectors can enhance the performance of the Savonius turbine.

This research aims a numerical and geometrical investigation about an Overtopping Device Wave Energy Converter (OTD-WEC). Constructal Design method was employed to perform a geometric evaluation of this OTD-WEC submitted to ocean waves with similar characteristics of the coastal region of Paraná State – Pontal do Paraná city in southern Brazil, located 41 km from the coast and 30 m water deep. It was analyzed two different significant wave heights, HS1 = 1.25 m and HS2 = 1.50 m. In each set, it were simulated 10 cases with different ramp angles, totaling 20 numerical simulations. The main goal was to evaluate the influence of the ramp angle on the water mass flow rate entering the reservoir. Therefore, through the Construtal Design, the degree of freedom (DOF) H1/L1 (ratio between the height and length of the ramp) was varied, considering a constant area of the ramp. For the numerical analysis, a two-dimensional computational model was employed using the commercial software Ansys Fluent, which is based on the Finite Volume Method (FVM). The multiphase Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The results showed that the best geometric configurations happened for those cases with smaller ramp angles. In addition, a reconfiguration of the ramp angles, keeping the area fixed, allowed a significant improvement in the OTD-WEC available power.

This research aims a numerical and geometrical investigation about an Overtopping Device Wave Energy Converter (OTD-WEC). Constructal Design method was employed to perform a geometric evaluation of this OTD-WEC submitted to ocean waves with similar characteristics of the coastal region of Paraná State – Pontal do Paraná city in southern Brazil, located 41 km from the coast and 30 m water deep. It was analyzed two different significant wave heights, HS1 = 1.25 m and HS2 = 1.50 m. In each set, it were simulated 10 cases with different ramp angles, totaling 20 numerical simulations. The main goal was to evaluate the influence of the ramp angle on the water mass flow rate entering the reservoir. Therefore, through the Construtal Design, the degree of freedom (DOF) H1/L1 (ratio between the height and length of the ramp) was varied, considering a constant area of the ramp. For the numerical analysis, a two-dimensional computational model was employed using the commercial software Ansys Fluent, which is based on the Finite Volume Method (FVM). The multiphase Volume of Fluid (VOF) model was applied to tackle with the water-air interaction. The results showed that the best geometric configurations happened for those cases with smaller ramp angles. In addition, a reconfiguration of the ramp angles, keeping the area fixed, allowed a significant improvement in the OTD-WEC available power.

A two-dimensional numerical study about the influence of a vertical distance between two ramps of an Overtopping Device Wave Energy Converter (OTD-WEC) integrated into a breakwater in the city of São José do Norte, Rio Grande do Sul, Brazil was analyzed. The main purpose was to evaluate the influence of the vertical distance between the two ramps (H_g) of OTD-WEC, on the average overtopping dimensionless flow () using the Constructal Design for the geometric evaluation defining: 1) degree of freedom, (H_g), and 2) constraints, horizontal distance between the ramps (L_g), ratio between the height and length of the ramps (H₁/L₁ and H₂/L₂), area as a function of the wave parameters (A_wave), areas of the ramps (A_r,i), maximum ramp height (fixed as half of the significant wave height (H_S/2) at the MWL) and area fractions of the ramps (φ_i). The equations of conservation of mass, momentum, and an equation for the transport of volumetric fraction were solved using the Finite Volume Method (FVM). The multiphase model Volume of Fluid (VOF) was applied for the air-water interaction. The results showed that, in general, lower values of the vertical distance between the ramps (H_g) led to higher values of the average overtopping dimensionless flow (). Moreover, the geometric evaluation of the degree of freedom H_g through the Constructal Design method proved to be an important tool because some configuration of the ramps of the overtopping device facilitated the flow of water to the reservoir of the device, and others made it difficult. The maximum value of the average overtopping dimensionless flow was _max = 0.044, with a difference of 2.23% for the value obtained with empirical equation found in the literature, for the vertical distance equal to H_g = 0.10.

A numerical study was performed in the present work about an Overtopping Device Wave Energy Converter (OTD-WEC) with one and two ramps incorporated in a real breakwater. The Constructal Design method was applied to evaluate the effects on the average dimensionless overtopping flow of the degrees of freedom of the device with one and two ramps. In addition, a comparison was carried out among the different geometry configurations of the OTD-WEC to determine which one presents the best hydrodynamic performance. The work used the JONSWAP spectrum and the multiphase Volume of Fluid model. It also solved the conservation equations for mass, momentum, and an equation for the transport of the volume fraction using the Finite Volume Method. Results showed that a device with a two-ramps configuration presented an average dimensionless overtopping flow 6.48% higher than those obtained for the one ramp. Present results obtained using Constructal Design theoretical recommendations about the influence of a complex configuration with four degrees of freedom over the performance of an OTD-WEC integrated into the east breakwater of the city of São José do Norte, State of Rio Grande do Sul (RS), Brazil.