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This article presents a numerical study encompassing the mechanical behavior prediction during the roll bending process applied to four distinct profiles of extruded 6061-T6 aluminum, considering different radii of curvature. The numerical simulations were conducted using the ANSYS® software, based on the finite element method, adopting the three-dimensional SOLID187 finite element. The employed computational model was developed and validated by Moreira et al. [1]. The obtained results demonstrate consistent patterns regarding stresses and displacements for the different radii of curvature. As the radius of curvature decreases, the von Mises stress tends to increase, approaching the material's strength limit. This phenomenon is critical for identifying points of maximum stress and ensuring adequate safety margins to prevent structural failures. Displacements along the profiles were also monitored, providing relevant information about its evolution at different radii of curvature and allowing curve fitting for these displacements in each profile investigated. Therefore, these consistent patterns observed can help to determine the direct influence of curvature on resulting defects, contributing to an in-depth understanding of the mechanical behavior of these profiles.

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.

Significance: The thermal analysis of nanofluid in a vertical cylinder (artery) in a magnetized environment holds significant implications in physiological and thermal regulation networks. This research is significant in biomedical engineering with applications like medical diagnostics and treatment strategies. Motive: This study investigates the thermal behavior of a magnetized blood-based ternary Carreau nanofluid flowing through a vertically bounded artery with quadratic convection. Velocity and heat transfer analysis is conducted within the artery, utilizing thermal radiation and quadratic convection in a magnetized setting. The base fluid consists of blood, augmented with three nanoparticles: CuO, Al2O3, and TiO2. The investigation centers on examining the properties of blood nanofluid, arterial geometry, and thermal dynamics. Methodology: The physical model generates a set of partial differential equations (PDEs) and similarities mechanism is utilized to fetch its non dimensional form in terms of ordinary differential equations (ODEs). Furthermore, numerical outcomes are obtained with Matlab function bvp4c and obtained data set is trained through robust scheme Levenberg-Marquardt neural network (LMNN) procedure to predict the solution. Findings: Velocity of blood is reduced with increased values of wiessenberg number, magnetic parameter and mixed convection parameter and velocity increases for Second-order convection parameter. Temperature profile decreases with curvature parameter, mixed convection parameter and permeability parameter.

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 study concentrates on numerically evaluating the behavior of a floating body with a box format. Although research on floating objects has been conducted, the numerical modeling of Wave Energy Converter (WEC) devices, considering the effects of fluctuations, remains underexplored. Therefore, this research intends to facilitate the analysis of floating devices. First, the experimental data served as a benchmark for evaluating the motion paths of the floating box’s centroid. Second, the effects of various wave periods and heights on the floating body’s movement were analyzed. The Volume of Fluid (VOF) multiphase model was applied to simulate the interactions between phases. The computational model involved solving governing equations of mass conservation, volumetric fraction transport, and momentum, employing the Finite Volume Method (FVM). The validation demonstrated that the Normalized Root Mean Square Error (NRMSE) for the x/h ratio was 3.3% for a wave height of 0.04 m and 4.4% for a wave height of 0.1 m. Moreover, the NRMSE for the z-coordinate to the depth of water (z/h) was higher, at 5% for a wave height of 0.04 m and 5.8% for a wave height of 0.1 m. The overall NRMSE remained within acceptable ranges, indicating the reliability of the numerical solutions. Additionally, the analysis of horizontal and vertical velocities at different wave periods and heights showed that for H = 0.04 m, the wave periods had a minimal impact on the amplitude, but the oscillation frequency varied. At H = 0.1 m, both velocities exhibited significantly larger amplitudes, especially for T = 1.2 s and T = 2.0 s, indicating stronger motion with higher wave heights.

This study presents a numerical evaluation of a Horizontal Rectilinear Earth–air Heat Exchanger (EAHE), considering the climatic and soil conditions of Viamão, Brazil, a subtropical region. The Constructal Design method, combined with the Exhaustive Search, was utilized to define the system constraints, degree of freedom, and performance indicators. The degree of freedom was characterized by the aspect ratio between the vertical and horizontal lengths of the elliptical cross-section duct (H/L). The performance indicators for the EAHE configurations were assessed based on thermal potential (TP) and pressure drop (PD). The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was applied for multi-objective evaluation, and a methodology for EAHE is proposed. The problem was solved using FLUENT software (version 2024 R2), which employs the Finite Volume Method to solve the conservation equations for mass, momentum, and energy. The (H/L)T,o = 6.0 configuration showed a 16.4% increase in thermal performance for heating and 15.9% for cooling compared to the conventional circular duct. Conversely, the (H/L)F,o = 1.0 configuration reduced pressure loss by 65.33%. The integration of Constructal Design with TOPSIS facilitated the identification of optimized geometries that achieve a balance between performance indicators and those that specifically prioritize thermal or fluid dynamic aspects, being this approach an original scientific contribution of the present work.

In this research, considering the air methodology, an axisymmetric model was developed, validated, and calibrated for the numerical simulation of an Oscillating Water Column (OWC) converter subjected to a realistic sea state, representative of the Cassino beach, in the south of Brazil. To do so, the Finite Volume Method (FVM) was used, through the Fluent software (Version 18.1), for the airflow inside the hydro-pneumatic chamber and turbine duct of the OWC. Furthermore, the influence of geometric parameters on the available power of the OWC converter was evaluated through Constructal Design combined with Exhaustive Search. For this, a search space with 100 geometric configurations for the hydro-pneumatic chamber was defined by means of the variation in two degrees of freedom: the ratio between the height and diameter of the hydro-pneumatic chamber (H1/L1) and the ratio between the height and diameter of the smallest base of the connection, whose surface of revolution has a trapezoidal shape, between the hydro-pneumatic chamber and the turbine duct (H2/L2). The ratio between the height and diameter of the turbine duct (H3/L3) was kept constant. The results indicated that the highest available power of the converter was achieved by the lowest values of H1/L1 and highest values of H2/L2, with the optimal case being obtained by H1/L1 = 0.1 and H2/L2 = 0.81, achieving a power 839 times greater than the worst case. The values found are impractical in real devices, making it necessary to limit the power of the converters to 500 kW to make this assessment closer to reality; thus, the highest power obtained was 15.5 times greater than that found in the worst case, these values being consistent with other studies developed. As a theoretical recommendation for practical purposes, one can infer that the ratio H1/L1 has a greater influence over the OWC’s available power than the ratio H2/L2.

This study numerically analyzes a submerged horizontal plate (SHP) device subjected to both regular and irregular waves. This device can be used either as a breakwater or a wave energy converter (WEC). The WaveMIMO methodology was applied for the numerical generation and wave propagation of the sea state of the Rio Grande coast in southern Brazil. The finite volume method was employed to solve conservation equations for mass, momentum, and volume fraction transport. The volume of fluid model was employed to handle the water-air mixture. The SHP length (Lp) effects were carried out in five cases. Results indicate that relying solely on regular waves in numerical studies is insufficient for accurately determining the real hydrodynamic behavior. The efficiency of the SHP as a breakwater and WEC varied depending on the wave approach. Specifically, the SHP demonstrates its highest breakwater efficiency in reducing wave height at 2.5Lp for regular waves and 3Lp for irregular waves. As a WEC, it achieves its highest axial velocity at 3Lp for regular waves and 2Lp for irregular waves. Since the literature lacks studies on SHP devices under the incidence of realistic irregular waves, this study significantly contributes to the state of the art.

This research conducts a numerical study of a wave energy converter (WEC) device with five coupled hydropneumatic chambers, operating based on the principle of an oscillating water column (OWC). A turbine was not included, only considering the tube without it. The computational domain was defined by a wave channel housing an OWC device subjected to regular incident waves. The central objective was to assess the impact of chamber geometry on maximizing the total hydropneumatic power in energy conversion. The numerical simulations consider the pressure, mass flow rate, and total hydropneumatic power, with the latter being the performance indicator. To determine the geometries to be analyzed, the Constructal Design method was employed in conjunction with the exhaustive search optimization method to maximize the performance indicator. The degrees of freedom defined were the ratios between the height (Hn) and the length (Ln) of the hydropneumatic chambers (Hn/Ln, where n varies from one to five). Based on the results of the mass flow rate and pressure, their influence on power was evaluated. It was observed that the influence of the degrees of freedom on the pressure difference, mass flow rate, and hydrodynamic power was quite similar, displaying an increase for low ratios of Hn/Ln up to a maximum magnitude and followed by a decrease in magnitude. The best performance was achieved for the geometric configuration with Hn/Ln = 0.2613 (Hn = 5.0625 m and Ln = 15.8219 m), representing an improvement of 98.6% compared to the worst case analyzed.

Liquid composite molding techniques are largely used to produce pieces such as truck cabins or wind turbine blades. The liquid resin infusion processes use a network of injection channels to improve the resin flow through a porous-reinforced medium. The present numerical study predicts the positioning of empty channels by applying constructal theory to an idealized problem. The channels’ position and size were not predefined but instead constructed (made to grow) from an elemental channel. Two strategies were tested for channel growth: each new elemental channel was placed next to the region with the lowest or highest resistance to resin flow. The geometric configuration of the channels was constructed using a control function instead of using pre-defined shapes. The conservation of mass and momentum and an additional transport equation for the resin volume fraction were solved using the finite volume method. The volume of the fluid model was used for the treatment of the multiphase flow (air + resin). The growth of an empty channel with the lowest resistance strategy led to a decrease in the injection time and waste of resin. The size (resolution) of the elemental channel also affected the performance indicators and geometric configuration of the injection channels.

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: H1/L is the ratio between the height and length of the hydropneumatic chamber, whose values were varied, and H2/l (ratio between height and length of the turbine duct) and H3 (submergence depth of hydropneumatic chamber) were kept constant. The best performance was observed for the device geometry with H1/L= 0.1985, which presented an available hydropneumatic power Phyd 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 H1/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 Phyd of 30.50 W was encountered.

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 Florianópolis, 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.

Constructal design, finite element method and exhaustive search are applied to analyze different arrangements of steel plates with rectangular or trapezoidal stiffeners. As performance parameters, the maximum deflection and maximum von Mises stress are considered. A non-stiffened plate adopted as reference is studied together with 25 plates with rectangular stiffeners and 25 plates with trapezoidal stiffeners. The results show that trapezoidal stiffeners are more effective in minimizing the maximum deflection in comparison with rectangular stiffeners. However, regarding the minimization of stress, the rectangular stiffeners normally present better performance. When both performance parameters are concomitantly considered, a slight advantage of 4.70% for rectangular geometry is identified.

Thin plates are widely used in various engineering applications. In some cases, these structural components may buckle due to compressive loads, which can be aggravated by lateral loads. Several authors have studied the elastoplastic buckling behavior of thin plates considering parameters such as material and geometric properties, support conditions, and initial out-of-plane imperfections. Some studies have also investigated the effects of notches and holes on the ultimate buckling stress of thin plates. The main goal of the present work is to verify and validate a computational model developed using the Finite Element Method via ANSYS® software, to simulate the mechanical behavior of metallic plates under uniaxial or biaxial compression combined with lateral load. The proposed numerical model was verified and validated by comparing its results with analytical, numerical, and experimental solutions found in the literature, reaching maximum differences and errors of around 5%. In sequence, the verified and validated computational model was used in a simple case study: a simply supported plate with a centered rectangular perforation and subjected to an in-plane compressive biaxial load combined with a lateral load, considering five different metallic materials: AISI 4130 steel, AH-36 steel, spheroidal graphite iron (SGI), compact graphite iron (CGI) and Al 7075-T651 aluminum alloy. The results obtained are consistent and, as expected, prove the applicability of the proposed computational model. From this, the biaxial elastoplastic buckling behavior was evaluated, indicating that among the studied cases the higher ultimate stress and the smallest maximum deflection were achieved, respectively, by the plates made of AISI 4130 steel and AH-36 steel.

In the constructal design method, the comprehension of the effect of design on the system performance is crucial to understanding the contributions of the degrees of freedom or constraints in the system evolution in direction of optimal configurations. However, problems with many degrees of freedom are prohibitive of optimization with exhaustive search, requiring meta-heuristic strategies. Therefore, the investigation of the optimization algorithms is essential. This work investigates the canonical differential evolution algorithm associated with the constructal design for the geometric optimization of an isothermal double Y-shaped cooling cavity inserted into a wall with internal heat generation. The effect of four degrees of freedom over the thermal performance of the system is investigated using sixteen different combinations of differential evolution algorithms: four variations of mutation parameter, two values of amplification factor (F) and two values of crossover rate (CR). The non-parametric statistical methods of Kruskal–Wallis and Dunn test were used to identify the parameters that improve the meta-heuristic efficiency. Results indicated that the proposed methodology selected the proper combination of DE algorithm parameters (CR, F, and mutation) that led to the best effect of degrees of freedom over the thermal performance in all optimization levels investigated.

The present work aims to define strategies for numerical simulation of the mixture of turbulent flows in a stirred tank with a low computational effort, and to investigate the influence of the geometry of four rectangular baffles on the problem of performance. Two computational models based on momentum source and sliding mesh are validated by comparison with experimental results from the literature. For both models, the time-averaged conservation equations of mass, momentum and transport of the mixture are solved using the finite volume method (FVM) (FLUENT® v.14.5). The standard k–ε model is used for closure of turbulence. Concerning the geometrical investigation, constructal design is employed to define the search space, degrees of freedom and performance indicators of the problem. More precisely, seven configurations with different width/length (L/B) ratios for the rectangular baffles are studied and compared with an unbaffled case. The momentum source model leads to valid results and significantly reduces the computational effort in comparison with the sliding mesh model. Concerning the design, the results indicate that the case without baffles creates the highest magnitude of turbulence kinetic energy, but poorly distributes it along the domain. The best configuration, (L/B)o = 1.0, leads to a mixture performance nearly two times superior than the case without baffles.

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.

The present work aims to develop a computational model investigating turbulent flows in a problem that simulates an oscillating water column device (OWC) considering a Savonius turbine in the air duct region. Incompressible, two-dimensional, unsteady, and turbulent flows were considered for three different configurations: (1) free turbine inserted in a long and large channel for verification/validation of the model, (2) an enclosure domain that mimics an OWC device with a constant velocity at its inlet, and (3) the same domain as that in Case 2 with sinusoidal velocity imposed at the inlet. A dynamic rotational mesh in the turbine region was imposed. Time-averaged equations of the conservation of mass and balance of momentum with the k–ω Shear Stress Transport (SST) model for turbulence closure were solved with the finite volume method. The developed model led to promising results, predicting similar time–spatial-averaged power coefficients (CP¯) as those obtained in the literature for different magnitudes of the tip speed ratio (0.75 ≤ λ ≤ 2.00). The simulation of the enclosure domain increased CP¯ for all studied values of λ in comparison with a free turbine (Case 1). The imposition of sinusoidal velocity (Case 3) led to a similar performance as that obtained for constant velocity (Case 2).

The growing global demand for energy and the costly taxes on electric energy demonstrate the importance of seeking new techniques to improve energy efficiency in industrial facilities. Refrigeration units demand a large amount of electricity due to the high power needs of the components of the system. One strategy to reduce the electric energy consumption in these facilities is pressure condensation control. The objective here was to develop a logical control model where the physical quantities in the thermodynamic process can be monitored and used to determine the optimum point of the condensation pressure and the mass flow rate of the air in the evaporative condenser. The algorithm developed was validated through experiments and was posteriorly implemented in an ammonia industrial system of refrigeration over a period of sixteen months (480 days). The results showed that the operation of the evaporative condenser with a controlled air mass flow rate by logical modeling achieved a reduction of 7.5% in the consumption of electric energy, leading to a significant reduction in the operational cost of the refrigeration plant.

The work presents a numerical study of a wave energy converter (WEC) device based on the oscillating water column (OWC) operating principle with a variation of one to five coupled chambers. The main objective is to evaluate the influence of the geometry and the number of coupled chambers to maximize the available hydropneumatic power converted in the energy extraction process. The results were analyzed using the data obtained for hydropneumatic power, pressure, mass flow rate, and the calculated performance indicator’s hydropneumatic power. The Constructal Design method associated with the Exhaustive Search optimization method was used to maximize the performance indicator and determine the optimized geometric configurations. The degrees of freedom analyzed were the ratios between the height and length of the hydropneumatic chambers. A wave tank represents the computational domain. The OWC device is positioned inside it, subject to the regular incident waves. Conservation equations of mass and momentum and one equation for the transport of the water volume fraction are solved with the finite volume method (FVM). The multiphase model volume of fluid (VOF) is used to tackle the water–air mixture. The analysis of the results took place by evaluating the performance indicator in each chamber separately and determining the accumulated power, which represents the sum of all the powers calculated in all chambers. The turbine was ignored, i.e., only the duct without it was analyzed. It was found that, among the cases examined, the device with five coupled chambers converts more energy than others and that there is an inflection point in the performance indicator, hydropneumatic power, as the value of the degree of freedom increases, characterizing a decrease in the value of the performance indicator. With the results of the hydropneumatic power, pressure, and mass flow rate, it was possible to determine a range of geometry values that maximizes the energy conversion, taking into account the cases of one to five coupled chambers and the individual influence of each one.

This paper presents a computer method to find the best sine-based function, in the sense of least squares, to fit periodic data. Even though the least squares method is not a novelty, there is a void in the literature about its use to find trigonometric functions, particularly when it gives rise to nonlinear systems, as it is done in this article. The respective code, implemented in the Matlab programming language, is detailed and analyzed exploring experimental data from the air and soil temperatures measured along the year in earth air heat exchangers (EAHE) built in the facilities of a case study house in the Brazilian state of Rio Grande do Sul. The fitting curves have been employed by the authors in different works to define boundary conditions to study new computer models of EAHE.

Relying on the Constructal Design method, this paper introduces new periodic models for the thermal potential of Earth-Air Heat Exchangers (Eahe). As a case study, it analyses the best spacing for three ducts arranged triangularly in order to maximize the heat transfer between soil and air. More specifically, the ratio between the horizontal and vertical spaces among the ducts is set free to vary up to limiting global constraints. This paper aims to better understand how the variations in affect the thermal performance of Eahe. As an additional contribution, some relationships between and the thermal potential of Eahe are mathematically and continuously stated. This allows establishing additional results for the efficiency and energetic performance of Eahe, as well as recommend arrangements in the shape of isosceles triangles with base and height unitary.

With over that 70% of the Earth submerged by seas, continents separated by oceans, two thousand major islands scattered throughout the World, hundreds of thousands of kilometers of navigable rivers, maritime or fluvial transport surely represents one of the most important ways of moving people, goods, and wealth around the globe [...]

Este estudo numérico utiliza o método Constructal Design para reduzir os pontos quentes de um sistema com geração de calor uniforme por unidade de volume através da transferência de calor por condução. A ideia é facilitar o acesso do fluxo de calor através de uma via em forma de “T” empregando condutividades térmicas não uniformes para a base e topo do T. A função objetivo consiste em minimizar o excesso de temperatura máxima adimensional de todo o sistema (materiais de alta e de baixa condutividade térmica). A configuração do sistema pode variar sujeita à duas restrições: o volume total e o volume das vias de alta condutividade. Materiais de várias condutividades e frações de áreas são estudados. Os resultados mostram a aplicabilidade do Constructal Design para a melhoria do desempenho térmico do sistema. Para o valor de condutividade térmica elevada a melhor geometria tende para uma forma de I (isto é, a parte superior, tende a diminuir, tornando-se semelhante à base). A otimização de um grau de liberdade reduziu em 18% o excesso de temperatura da melhor configuração quando ela é comparada com a pior configuração.

Este artigo aplica o Design Construtal para avaliar a geometria de um canal em forma de T submetido a um escoamento com convecção forçada com o objetivo de maximizar a taxa de transferência de calor. A temperatura das paredes do canal é mantida constante, superior à de entrada do escoamento forçado. O volume do canal em forma de T é uma constante do problema. Além disso, o sistema é submetido a três graus de liberdade: H1/L0 (razão entre a altura do ramo secundário e a largura do ramo principal), H0/L1 (razão entre a altura do ramo principal e a largura do ramo secundário) e H0/L0 (razão entre a altura do ramo principal e a largura do ramo principal). Para todos os casos é considerado um escoamento laminar, incompressível, permanente, com transferência de calor por convecção forçada. A avaliação geométrica é realizada para três números de Reynolds: ReL,c= 10, 100 e 1000. Assim, a influência desse parâmetro sobre a avaliação geométrica também é avaliada. Para todos os casos, considera-se um número de Prandtl constante (Pr = 0,71). As equações de conservação de massa, quantidade de movimento e energia são resolvidas com o Método de Volumes Finitos (MVF). A melhor geometria conduziu a um desempenho 160% superior do que a pior geometria avaliada para um mesmo Número de Reynolds. Os estudos realizados permitiram mostrar a importância da aplicação do Design Construtal associado, neste trabalho, ao método de Busca Exaustiva, para a otimização geométrica de problemas de engenharia. Foi observado também que entre os casos estudados não há uma geometria ótima universal que conduza ao melhor desempenho térmico do problema estudado.

O fenômeno de flambagem ocorre quando elementos estruturais esbeltos são submetidos a cargas de compressão axial. Além disso, em muitas situações é necessário que existam perfurações nestas placas. Neste artigo o método Constructal Design, baseado na Teoria Constructal, foi utilizado para avaliar a influência da geometria do furo em placas finas de aço submetidas à flambagem elástica. Para isso, furos do tipo retangular, elíptico e oblongo, centralizados na placa, foram considerados. A geometria desses furos foi variada considerando o grau de liberdade H0/L0, que relaciona as dimensões características de cada tipo de perfuração. Além disso, todos os furos analisados possuem a mesma fração de volume (), que representa a relação entre o volume da perfuração e o volume da placa sem furo. A função objetivo é maximizar a carga crítica das placas perfuradas. Para tanto, o software ANSYS, baseado no Método dos Elementos Finitos (MEF), foi empregado para determinar numericamente a carga crítica de flambagem em cada caso. Foi observada a importância da configuração geométrica nas busca por performances superiores: através de uma simples variação na geometria do furo, mantendo fixa sua fração volumétrica, foi possível obter cargas críticas até 143,40 % superiores quando comparados às obtidas com as piores geometrias.

A crescente necessidade de estruturas com propriedades mecânicas superiores impulsiona o desenvolvimento de novos tipos de materiais, dentre os quais se destacam os materiais compósitos laminados reforçados por fibras. Placas finas construídas com estes materiais possuem diversas vantagens em comparação com as fabricadas com materiais de construção mecânica convencionais como o aço: altas relações rigidez/peso e resistência/peso; alta resistência à fadiga; e excelente resistência à corrosão. Portanto, a aplicação destes elementos estruturais é cada vez mais frequente em diversas áreas da engenharia, especialmente em estruturas navais e offshore. Neste contexto, o presente trabalho analisa numericamente o comportamento mecânico de placas finas fabricadas com diferentes tipos de materiais compósitos (Vidro-E / Epóxi, Boro / Epóxi, Tecido de Vidro / Epóxi e Boro / Alumínio) em comparação com o comportamento mecânico de uma placa de Aço. Os resultados mostraram que é possível obter com uma placa de material compósito reforçado por fibras um comportamento mecânico semelhante, ou até melhor, que o de uma placa de aço.

Placas são elementos amplamente empregados na engenharia estrutural. Em muitas situações é necessária a existência de perfurações nestas placas. Sabe-se ainda que elementos estruturais esbeltos submetidos a cargas de compressão axial podem falhar de maneira súbita, com uma tensão inferior à tensão de escoamento do material, devido a um fenômeno de instabilidade conhecido como flambagem. Nesse artigo, a Teoria Constructal será utilizada para otimizar geometricamente placas finas perfuradas, submetidas a compressão uniaxial, tendo como objetivo obter a dimensão ótima do furo que maximize a carga crítica de flambagem. Para isso diversas simulações numéricas foram realizadas, utilizando um modelo computacional baseado no Método dos Elementos Finitos (MEF). Observou-se que para todos os valores de Ø (relação entre o volume do furo e o volume da placa) analisados, a placa que apresenta melhor desempenho sob compressão uniaxial é a que possui a maior relação H/L (relação entre a altura e o comprimento da placa). No que diz respeito à análise individual de cada placa, a que obteve o maior acréscimo percentual no valor de carga crítica de flambagem em relação a uma placa sem furo foi a placa 1 (H/L = 1.00), chegando a 198.98%. A placa que apresentou o menor acréscimo percentual foi a placa 4 (H/L = 0.25), com 7.72%. Ao realizar uma comparação global entre as placas, a que obteve o melhor desempenho foi a placa 1 (H/L = 1.00), apresentando uma carga crítica máxima de flambagem 176.85% maior que a carga crítica máxima na placa de pior desempenho, placa 4 (H/L = 0.25).

O presente trabalho apresenta um estudo teórico a respeito da influência de diversos perfis aerodinâmicos (NACA0012, NACA0015, NACA0018, NACA0020 e NACA0021) sobre a potência e torque gerados em uma turbina Wells. Em todos os casos avaliados, o rotor possui um raio da turbina rt = 245 mm e uma razão de aspecto de AR = 0.7. O objetivo principal é obter uma recomendação teórica a respeito de qual perfil aerodinâmico pode ser empregado para os rotores de pequenos dispositivos de conversão de energia das ondas do mar em energia elétrica, mais especificamente coluna de água oscilante com potências inferiores a 1 kW. Para realizar a estimativa da potência e torque foram utilizadas recomendações teórico-experimentais da literatura. Os resultados indicaram que o melhor perfil aerodinâmico (NACA0021) é capaz de conduzir a uma potência mecânica de aproximadamente 319 W, apresentando um desempenho 36 % superior ao perfil NACA0020, que conduziu aos piores resultados.

Este artigo considera o design constructal de um corpo cilíndrico sólido arrefecido por duas aletas na forma T. O objetivo é minimizar o máximo excesso de temperatura entre o corpo cilíndrico e sólido a temperatura ambiente. A geração interna de calor é distribuída uniformemente em todo o corpo sólido. As aletas de são banhadas por uma corrente constante, com temperatura ambiente constante e transferência de calor por convecção. As superfícies exteriores do corpo cilíndrico são adiabáticas. O volume total do corpo e o volume total do conjunto de aletas são fixos, mas a espessura e comprimento das aletas podem variar. A geometria otimizada e o desempenho são reportados graficamente como funções da relação entre a espessura e a razão entre os comprimentos das aletas. É também digno de que, quando comparada com uma configuração com um único conjunto de aletas na forma de T a configuração com duas aletas na forma de T realizam aproximadamente 50% melhor o seu desempenho

Este artigo apresenta um modelo computacional bidimensional desenvolvido para análise do quebra mar tipo placa submersa. O modelo desenvolvido utiliza os códigos comerciais GAMBIT e FLUENT. O escoamento da mistura água-ar nas simulações numéricas do dispositivo é realizada através do modelo multifásico Volume of Fluid. O objetivo deste artigo é contribuir para um maior conhecimento deste dispositivo mostrando seu bom desempenho nas funções de quebra mar e conversor de energia das ondas. É analisada a influência da posição vertical da placa no coeficiente de transmissão e na eficiência do dispositivo ao converter energia das ondas em energia elétrica. Para tanto, o modelo desenvolvido, depois do processo de validação, foi utilizado em seis simulações que diferem apenas na posição da placa. Nos casos estudados, o aumento da distância da placa ao fundo proporcionou aumento da eficiência e redução do coeficiente de transmissão.

Este artigo tem por objetivo avaliar qualitativamente os resultados numéricos obtidos utilizando-se CFD para modelagem de condensadores evaporativos. Compara-se resultados da literatura com aqueles obtidos a partir de um condensador evaporativo de pequena escala, para testes em laboratório. Os campos de pressão e velocidade foram avaliados. Os resultados mostraram-se coerentes com aqueles apresentados na literatura. Dois ângulos de entrada de ar foram testados: 0° and 45° em direção ao reservatório de água. Foi observado uma pequena influência do ângulo de entrada de ar sobre o fluxo mássico de ar na saída. Estudos futuros podem ser realizados no sentido de melhorar a distribuição de ar dentro do equipamento a fim de aumentar a sua eficiência térmica.

The present work presents a study concerned with the project of a wind turbine. This task is basically shared in two steps. The first one is the blades aerodynamic project, with the purpose of taking more advantage of the wind kinetic energy and the second one is concerned with the mechanical project of the blades, in order to support the loads over the blades during the operation period. The graphical modeling and the mechanical project of the blades are performed with the computational softwares AutoCad® and Excel. The commercial code Ansys® is employed to analyze the mechanical resistance and the reliability of the blade. To perform the prediction of the wind action efforts over the blade is used the aerodynamic analysis including forces, such as: axial, tangential, weight and centrifugal ones, and aerodynamic momentum. The blades are composed of fiberglass shell reinforced with plastic material. Vertical and horizontal reinforcements of wood and carbon fiber, respectively, are also employed.

The present work studies the geometric optimization of a body submitted to intense heat flux. The body to be optimized is refrigerated by a ducts system whose circulating fluid will remove the heat. The optimization method is denominated "Constructal Design" and it is based on Constructal theory", which is a new theory that guides the engineers in the discovery of new and highly efficient architectures for the drainage of fluids, mass, energy, and " anything that moves ". The maximum temperature of the system is minimized while the volumes of the body and of the fluid are maintained constant. However, the angle, diameters and lengths of the studied geometry can vary. The ducts structure to be studied is bifurcated. The flow in the ducts is considered incompressible, constant properties, laminar and threedimensional. The equations of conservation of the mass, momentum and energy are solved for the fluid, while the equation of the energy is solved for the solid. The numeric method uses finite volumes for the discretization of the conservation equations. Those equations are solved simultaneously for the determination of the temperature field.

The present work studies numerically and experimentally the water cooling process by means of natural convection inside a closed reservoir. The cooling process is performed by Peltier or Thermoelectric effect. The purpose here is to obtain the thermal gradient inside the reservoir and to search for the best point where the coldest water can be extracted from the reservoir, which can be considered a geometric optimization of the device thermal design. The analyzed flow is incompressible, laminar, transient and three-dimensional. The Boussinesq approximation is employed for the treatment of buoyancy forces. For the numerical approach of the flow, the mass, momentum and energy conservation equations are solved by a commercial package based on the finite volume method (FLUENT®). The temperature field as function of time obtained by numerical simulations is confronted with the experimental data. The numerical results estimated satisfactorily the transient thermal behavior predicted by laboratory experiments.

Este trabalho apresenta a modelagem computacional de um conversor de energia das ondas do mar em energia elétrica do tipo Coluna de Água Oscilante (CAO) submetido ao clima de ondas da costa da cidade de Rio Grande. A simulação numérica foi realizada utilizando-se o pacote FLUENT® e empregando-se o modelo multifásico Volume of Fluid (VOF) na geração da onda e na interação da mesma com o conversor. O domínio computacional foi representado por um tanque de ondas acoplado ao dispositivo CAO, possibilitando analisar o seu comportamento quando sujeito a incidência de ondas regulares com características semelhantes ao clima de ondas na costa de Rio Grande. Os resultados obtidos demonstram a potencialidade da região em gerar energia elétrica a partir da energia das ondas do mar, através do conversor tipo CAO.

The present work studies the optimization of a circular body with an intense heat flux by Constructal Design. The problem concerns the minimization of the global thermal resistance of a three-dimensional structure submitted to an intense uniform heat flux, which is cooled through micro-channels inserted in the circular body. For the optimization the body and the channels volumes are kept constants, while the geometrical configuration varies. Two geometric configurations were studied: radial and with one level of bifurcation - the first construct. The conservation equations of mass, momentum and energy are solved using a commercial package based on the finite volume method. For the radial configuration the system was successfully optimized as function of the number of ducts intruded into the body. For the bifurcated configuration Constructal Design led to a double optimization: one as function of the angle between the branches on the bifurcation () and other as function of the ratio between the length of a single duct (L0) and the radius of the circular domain (L).

The present paper applies Constructal Design to optimize the geometry of a Yshaped negative fin that intrudes a solid conducting wall with heat generation. The main goal is the minimization of the thermal global resistance between the solid wall and the negative fin, which removes energy from the wall. The optimization is achieved by varying the angle between the tributary branch of the Y-Shaped fin and the horizontal axis, as well as, by varying the ratio between the volume of the fin and the rectangular volume that circumscribes it (ψ), while the other geometric parameters are maintained fixed. Constructal Design led to a best configuration, with a thermal global resistance of 53%, 49% and 48% for ψ = 0.3, ψ = 0.4 and ψ = 0.5, respectively, smaller than the ones for the worst configuration.

Abstract Perforated steel thin plates are commonly used in structural engineering. Due to their geometric characteristics, these panels can suffer the undesired buckling phenomenon. In this context, the present work associates the computational modeling and the constructal design method to evaluate the influence of the geometric configuration in the plate buckling behavior, using the exhaustive search method to determine which geometries conduct to superior mechanical behavior. To do so, numerical models are employed to solve elastic and elasto-plastic buckling of plates having a centered perforation. Different hole types (longitudinal oblong, transversal oblong, elliptical, rectangular, diamond, longitudinal hexagonal, or transversal hexagonal) with different shapes (variation of characteristics dimensions of each hole type) are analyzed. Limit curves to avoid buckling were obtained, as well as the definition of the geometries that can improve up to 107% the plate performance.