Transport phenomena, which involve the transfer of momentum, energy, and mass, underlie a wide range of problems in numerous engineering fields, including environmental, civil, mechanical, chemical, energy, and aerospace engineering [...]

O presente trabalho consiste na construção de um modelo numérico de um escoamento turbulento, permanente, bidimensional, incompressível e com convecção forçada ao longo de um micro canal com paredes com corrugações em formato trapezoidal. O caso é simulado para escoamentos convectivos com números de Reynolds e Prandtl iguais a ReD = 22.000 e Pr = 0,71. As equações temporais médias de conservação de massa, quantidade de movimento e energia são resolvidas através do Método dos Volumes Finitos implementado no software Ansys Fluent. A abordagem RANS (Reynolds Averaged Navier-Stokes) com modelo k - ω SST (Shear Stress Transport) é empregada na modelagem da turbulência. Ao final do estudo foi possível obter um modelo numérico capaz de predizer o escoamento em micro canais com corrugações trapezoidais. Além disso, se observou que a direção da corrugação tem influência direta na perda de carga e troca térmica. As corrugações que estão direcionadas para fora do domínio não contribuem para a troca térmica, mas sim para a perda de carga. Enquanto as corrugações voltadas internamente para o domínio são as que mais contribuem para a troca térmica.

O presente estudo numérico tem como objetivo determinar a disposição ótima de aletas inseridas de forma alternada em microcanais, a fim de conduzir a máxima taxa de transferência de calor e a mínima perda de carga no canal. O escoamento no canal é de ar em menor temperatura, laminar, incompressível e em regime permanente, com transferência de calor por convecção forçada. O método design construtal é usado para o desenvolvimento das alternativas de projeto e o método TOPSIS é utilizado para avaliar os resultados de forma multiobjetiva, a partir de um indicador de performance multiobjetivo (Ci), baseado em uma ponderação de pesos para variável térmica e fluidodinâmica. No presente estudo são investigadas as razões entre as distâncias das aletas 1 e 2 e o comprimento da área de ocupação (L1/L e L2/L), enquanto as aletas 0 e 3 são mantidas fixas (L0/L = 0,125 e L3/L = 0,875). Todas as simulações numéricas foram conduzidas considerando um escoamento de ar com números de Reynolds e Prandtl constantes, ReH = 100 e Pr = 0,71, respectivamente. Os resultados indicaram que, ao atribuir um peso de 50% para cada indicador de desempenho, a geometria que apresenta os maiores valores de Ci possui configuração assimétrica com distância entre aletas não uniforme.

The demand for efficient thermal management technologies is increasing as chip technology advances and largescale data centers grow. High-conductivity fins and cavities are widely employed to enhance heat transfer. However, identifying the best fin or cavity configuration and understanding how it improves thermal performance remains a challenge. In this context, constructal design has been extensively applied to develop flow architectures that enhance access to internal flow and reduce thermodynamic imperfections. This work systematically reviews the evolution and application of constructal design in heat transfer problems involving fins and cavities. A total of 195 research articles from two major databases were analyzed. This study shows how fin and cavity designs have evolved and how these changes have influenced heat transfer performance. A bibliometric analysis also illustrates the growth of this research field and identifies recent research trends. Cavity geometries evolved from simple I-shaped cavities to complex branching configurations, including H-, X-, doubleY-, and tree-shaped designs. Under the same comparison conditions, the best-performing isothermal cavity was the tree-shaped configuration with four branches, which reduced the dimensionless maximum excess temperature by up to 93.6% compared with the baseline I-shaped cavity. Several fin configurations were also evaluated, including disk-shaped, circular, tree-shaped, Y-shaped, rectangular, and pin-fin arrays. The results indicate that the transition from simple fin geometries to hierarchical and branching designs improves thermal performance. The research field continues to grow, with recent studies focusing on mixed and forced convection and the application of constructal design to thermal energy storage systems with phase change materials.

Employing the WaveMIMO methodology, the present numerical study evaluates a submerged horizontal plate (SHP) device under the incidence of representative regular and realistic irregular waves associated with the sea state off the coast of Rio Grande, Brazil. The dual functionality of the SHP device is investigated, considering its operation as a breakwater (BW) and as a wave energy converter (WEC). The main focus of this study is to investigate the effects of numerical beach (NB) positioning on the hydrodynamic response of the SHP. The governing equations for mass, momentum, and volume fraction are solved using the finite volume method (FVM), while the water-air interaction is modeled through the volume of fluid (VOF) approach. The analysis assessed the influence of SHP length (Lp) using five different values. For the tested Rio Grande sea state, SHP geometry, two-dimensional numerical model, and adopted hydrodynamic indicators, the results show that the exclusive use of representative regular waves was not sufficient to reproduce the hydrodynamic trends obtained under realistic irregular waves. The SHP demonstrates its highest BW performance in reducing the significant wave height at 3Lp for representative regular waves and realistic irregular waves. As a WEC, it achieves its highest axial velocity at 3Lp for representative regular waves and 1.5Lp and 2Lp for realistic irregular waves. The performance of the SHP as BW-WEC is the highest at 3Lp for regular waves and 2.5Lp for realistic irregular waves. In contrast to previous work, in which the NB was kept at a fixed position, the present study indicates that the downstream computational-domain configuration, including the relative positioning between the SHP and the NB, is an important factor affecting the monitored hydrodynamic response and should be carefully defined in CFD wave-flume simulations.

O presente trabalho tem por objetivo avaliar numericamente um Trocador de Calor Solo-Ar Horizontal Helicoidal (TCSA-HH), considerando características climáticas e do solo do município de Viamão, RS, Brasil. A geometria do sistema é avaliada por meio da variação do passo entre as helicoides (Ph) do TCSA. O parâmetro utilizado para a análise do desempenho das diferentes configurações do TCSA-HH é através da avaliação do potencial térmico (PT) do sistema. O problema é solucionado numericamente utilizando o software FLUENT, que emprega o Método dos Volumes Finitos para resolver as equações de conservação de massa, quantidade de movimento e energia. Como resultado, os TCSAs-HH mostram-se apropriados para resfriamento do ar durante períodos quentes, embora a capacidade de aquecimento se apresente irrelevante em períodos frios. O TCSA-HH com Ph = 100 mm obteve o melhor desempenho relacionado ao PT, superando em aproximadamente 10% o TCSA-HH com Ph = 400 mm, que apresentou o pior desempenho térmico. Comparado a outros TCSAs presentes na literatura, o TCSA-HH apresentou um desempenho similar para condição de resfriamento, demonstrando ser uma alternativa viável para terrenos compactos.

Dentre as diversas fontes de energia renovável que podem ser exploradas, têm-se a energia contida nas ondas do mar, que pode ser extraída por meio de dispositivos conversores, como o do tipo Galgamento. Seu princípio operacional consiste em uma rampa que direciona as ondas incidentes para um reservatório; após, a água armazenada retorna ao oceano passando por turbinas de baixa-queda, que ativam um gerador de energia elétrica. Nesse sentido, o presente estudo realiza uma avaliação geométrica de um dispositivo de Galgamento, analisando a influência da razão entre a altura e o comprimento da rampa do dispositivo sobre a potência disponível. Além disso, investigou-se a influência do uso da condição de contorno de pressão de saída (CCPS) no fundo do reservatório do dispositivo. O software ANSYS Fluent foi utilizado a fim de realizar simulações numéricas de geração e propagação das ondas regulares representativas do estado de mar referente ao município de Rio Grande, no Rio Grande do Sul. Desse modo, constatou-se que a CCPS afeta o monitoramento dos resultados, recomendando-se que a mesma não seja utilizada. Além disso, por meio do Design Construtal, foi possível encontrar a geometria que maximizou o desempenho do conversor, obtendo uma potência disponível mais de 5 vezes superior à obtida pela pior configuração geométrica avaliada.

The Earth-Air Heat Exchanger (EAHE) can significantly reduce electricity consumption associated with building heating or cooling. However, its thermal performance may deteriorate during prolonged operation owing to the progressive thermal disturbance of the soil surrounding the buried duct. Phase Change Materials (PCM) have been integrated into EAHE systems to mitigate this issue, leading to improved thermal performance. Nevertheless, the influence of PCM-cylinder diameter on the coupled thermal, fluid-dynamic, and energetic behavior of concentric EAHE-PCM systems has not yet been systematically investigated. In this research, a 3D numerical model of an EAHE coupled with cylindrical PCM was developed using the climate and soil conditions of Viamão, Brazil, in ANSYS Fluent, a software based on the finite volume method (FVM). The influence of PCM-cylinder diameter was evaluated under identical operating conditions while maintaining constant Reynolds number and constant heat-transfer area. Validation and verification were carried out through comparisons with previous studies under similar climatic conditions. Results showed that the annual average thermal potential increases quadratically with increasing PCM-container diameter, and consequently with the amount of PCM. An enhancement of up to 150.84% and 96.40% was achieved for air heating and cooling, respectively. Although the fan power (Ẇ) increased exponentially from 0.000512 W to 0.262 W, it remained orders of magnitude smaller than |Q̇|. As a result, the calculated net power gain also increases with PCM volume, reaching approximately 174 W in heating and 193 W in cooling for the best case, demonstrating that the additional energy captured through enhanced thermal exchange outweighs the increase in fan power. Furthermore, the proposed volume-normalized thermal-performance indicator revealed diminishing incremental thermal benefits per unit PCM volume as the PCM-cylinder diameter increased. The combined analysis of thermal, hydraulic, and energetic indicators provides a more comprehensive assessment of the influence of PCM-cylinder geometry on concentric EAHE-PCM systems than considering thermal enhancement alone.

Thin plates are widely used and can be subjected to combined loads that trigger elasto-plastic buckling. Often, these plates are perforated, which significantly changes their mechanical response. This study investigates six perforation geometries (elliptical, longitudinal hexagonal, transverse hexagonal, longitudinal oblong, transverse oblong, and rectangular) and their influence on the ultimate buckling stress of perforated plates under biaxial compression and lateral pressure. Three plates with a distinct width b and length a ratio (b/a) and five unperforated plate volume and perforation volume ratios (ϕ) are analyzed using finite element analysis in ANSYS®, combined with Constructal Design, Exhaustive Search, and the Technique for Order Preference by Similarity to an Ideal (TOPSIS). Perforation geometry is shown to be a decisive parameter: elliptical perforations are the most efficient, limiting strength loss in rectangular plates with b/a = 1/3 and ϕ = 0.025 to about 6%, while oblong perforations cause reductions of up to 14%. In square plates (b/a = 1), elliptical perforations preserve more than 98% of the original strength for ϕ ≤ 0.05 and over 90% at ϕ = 0.20. TOPSIS results highlight configurations that balance small reductions in ultimate buckling stress with up to 23% lower maximum deflection, providing practical design guidelines.

Earth–Air Heat Exchangers (EAHEs) are passive systems that use the thermal interaction between air and soil along buried ducts to moderate supply air temperature, thereby lowering building energy consumption and improving indoor comfort conditions. This device has been employed in several countries and under diverse climatic characteristics. The integration of EAHE systems with bioclimatic design strategies contributes to improved building energy performance and more efficient use of thermal resources. This study aims to computationally investigate the thermoenergetic performance of EAHE system, for both cooling and heating purposes, installed in Social Housing (SH) across different Brazilian bioclimatic zones, and to propose strategies that improve the energy efficiency of these built environments. The study involves the validation and verification of a computational model and the thermoenergetic assessments of an SH unit, investigating different solar orientations and the installation of EAHE. These evaluations are performed via dynamic simulations conducted with the EnergyPlus software. The results show that the installation of the EAHE system coupled to the SH improves the thermoenergetic performance of the indoor environment, mainly by enhancing thermal comfort across different Brazilian bioclimatic zones (BZ). In BZ2R, the EAHE increased the annual PHFT by 4.5%, corresponding to seventeen additional days per year within the acceptable operative temperature range. The highest monthly improvement was observed in BZ1M, where the PHFT increased by 14.3% in January, equivalent to more than four additional days of thermal comfort in that month. The system proved to be more effective in zones 1M, 2R, 3B, and 4B, particularly in climates with lower annual average dry-bulb temperatures. Regarding energy performance, the EAHE showed benefits in specific months and conditions, indicating that its feasibility should be assessed through monthly thermoenergetic analyses rather than only annual indicators. This work provides validated and verified references and parameters for future projects and contributes to the state of the art in this field, as there are still few studies evaluating EAHE systems integrated into buildings using this software, despite its widespread use in building performance analysis.

This study presents a numerical investigation of thermo-bioconvection in oxytactic bacteria suspended within a trihybrid nanofluid, with a focus on advancing sustainable thermal management strategies for environmental and energy-efficient applications. The working fluid incorporates a blend of three distinct nanoparticles (Al2O3, TiO2, and others) dispersed in a base fluid, engineered to enhance thermal conductivity while minimizing energy consumption and environmental impact. This approach aligns with green technology principles by utilizing nanomaterials to improve heat transfer efficiency in low-energy systems. The interaction between thermal gradients and oxytactic bacterial motility is analyzed under the synergistic effects of buoyancy-driven convection and nanoparticle-induced thermal enhancement, both key mechanisms for sustainable energy utilization in microfluidic and biomedical systems. The governing partial differential equations for momentum, energy, and concentration fields are solved numerically using an energy-efficient computational scheme, reducing computational resource demands. Parametric analysis explores the effects of nanoparticle volume fraction, thermal conductivity ratio, and bacterial motility rate on heat and mass transfer, offering insights for designing eco-friendly thermal control systems. Results demonstrate that trihybrid nanoparticles significantly boost heat transfer, with the Nusselt number increasing by up to 7.5%, largely due to the synergistic effects of Al2O3 and TiO2. Enhancing the Reynolds number (Re) further amplifies convective performance, with observed increases of 12.4% in Nu and 48.2% in CfRe, indicating reduced thermal resistance and improved system efficiency. Additionally, applying a magnetic field results in a 5.6% improvement in thermal transport, showcasing another controllable, energy-saving factor. Notably, changes in the bioconvection Rayleigh number exhibit minimal influence (< 0:5%), suggesting operational stability under varying biological conditions. These findings underscore the potential of trihybrid nanofluids, combined with microbial motility and magnetic control, as environmentally sustainable and energy-efficient solutions for next-generation thermal management in biomedical devices, microchannel heat exchangers, and other green engineering applications.

Present work proposes a methodology based on constructal theory to guide the growth and design of empty channels embedded within rectangular porous plates. The channels design is constructed from an elementary configuration, following two performance indicators (the filling time, t, and the wasted resin mass, m) and employing exhaustive search to define the adjacent possible position of each new empty square element. The low resistance channels are constructed by solving numerically the fluid flow problem and determining which direction is easier to flow. Then, starting from an inlet vent and dividing the porous domain into small regions, the channel is made to grow (occupy adjacent squares) in direction to minimize the resin injection filling time (tm) or the wasted resin mass (mm). The results demonstrate that the methodology based on the constructal theory is promising for improving the flow system dynamics and enhancing the understanding of form development in such systems. It was also indicated that complex branched injection channel configurations led to tmin, regardless of the height/length ratio of the plate. The resulting patterns resembled natural configurations observed in pointto-volume flows with configuration adapted to the imposed area constraint. On the other hand, simple channel configurations conducted to mm.

This study conducts a numerical investigation of the geometry of the oscillating water column (OWC) wave energy converter under realistic irregular wave conditions found off the coast of Rio Grande, southern Brazil. Two OWC models were compared: the conventional design and the L-shaped configuration (L-OWC). The OWC structure consists of a hydropneumatic chamber and an air duct, where a turbine is coupled to an electric generator. Additionally, in the L-shaped chamber configuration, a water intake duct is considered. The constructal design method was employed for the geometric evaluation of the devices. For the L-OWC, the influence of the height-to-length ratio of the water intake duct on the obtained hydropneumatic power available was analyzed. In parallel, for the conventional OWC, the free-board submergence was investigated. Subsequently, the optimal geometry for each OWC model was selected to study the height-to-length ratio of the hydropneumatic chamber. Numerical simulations were performed using ANSYS Fluent software. Thus, the performance of the converters was improved by approximately 35.76 times for the L-OWC and 3.78 times for the conventional OWC. However, it is noteworthy that the optimal configuration of the conventional OWC achieved a performance 2.62 times higher than the optimal L-OWC geometry.

This numerical work presents a geometrical investigation of a corrugated isothermal surface placed in a twodimensional cavity subjected to unsteady, turbulent pool boiling flows. The main purposes are maximizing the heat transfer rate between the isothermal surface and the surrounding water flow, and the volume of vapor generated into the cavity. The geometric investigation followed the constructal design method, being the ratio Hi/Li (i = 1, 2 or 3) of the corrugations varied for three different numbers of corrugations: N = 1, 2, and 3, keeping constant the corrugations area. The volume of fluid (VOF) and Lee's evaporation-condensation models are used to estimate the volume fractions of water vapor/liquid and interfacial mass transfer. The unsteady Reynolds Averaged Navier Stokes (URANS) continuity, momentum and conservation of energy equations, and volume fraction transport equation, are solved using the finite volume method (FVM) available in software Ansys FLUENT. For closure of turbulence, the k - epsilon model is adopted. For validation of the model, the heat flux and convection heat transfer coefficient obtained for a pool boiling bared surface case are compared with Rohsenow's correlations, and differences lower than 7.0 % are reached. Results indicated a strong influence of the ratio Hi/Li and number of corrugations (N) in the heat transfer rate per unit depth (qs) and dimensionless volume of vapor (Vdim) generated into the cavity. The highest intrusion of the corrugations led to the generation of few large and many small scales, benefiting the thermal performance, regardless of the performance indicator employed. The optimal configuration, N = 3 and H3/L3 = 2.0 improved 49 % and 188 % the Vdim and qs compared with the worst corrugated case, showing the importance of the geometry of the corrugation in this problem.

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.

The present work investigated numerically turbulent airflows over a hybrid Darrieus/Savonius vertical axis wind turbine. Firstly, the isolated turbines were validated in comparison to previous studies from the literature. Later, new recommendations were obtained for the simulation of a hybrid turbine subject to turbulent airflow. The numerical simulations consisted of the solution of time-averaged equations of mass and momentum in x and y directions using the finite volume method, available in the commercial code Ansys Fluent (version 2022 R1). For closure of turbulence, the k − ω SST (Shear Stress Transport) model was employed. For lower magnitudes of tip speed ratio (TSR), the hybrid turbine improved the power coefficient (CP) compared to the Darrieus turbine (e.g., by 70% at TSR = 0.75), thereby demonstrating the self-starting capability of the hybrid configuration. Unexpectedly, at the optimal TSR = 1.5, the hybrid turbine performed about 6.5% better than the Darrieus turbine, indicating that the balance between the additional power generated by the Savonius rotor and losses caused by flow disturbances in the hybrid configuration was positive. As a novelty, results highlighted the role of each rotor (Darrieus and Savonius) for the performance of the hybrid turbine by comparing it with isolated Darrieus and Savonius turbines under the same conditions.

Thin steel plates with stiffeners are widely used in shipbuilding, aeronautics, and civil construction due to their lightness and structural strength. This study presents a numerical model developed using ANSYS Mechanical APDL with SHELL281 finite elements to evaluate the deflection of thin steel plates with trapezoidal-shaped box-beam stiffeners, known as hat-stiffened plates. The structure is analyzed under a uniformly distributed load perpendicular to the plate, with simply supported boundary conditions. The constructal design method combined with the exhaustive search technique is employed to optimize the geometry. A volume fraction of 30% is used, transferring material from the reference plate (without stiffeners) to the stiffeners, defining parameters such as number, height, and thickness—considered degrees of freedom. The stiffener angle is fixed at 120°. The results show that increasing stiffener height and reducing thickness generally improve structural performance by reducing deflections. The best configuration with transverse stiffeners reduced deflection by 97.15% compared to the reference plate, and by 79.27% compared to the best longitudinal configuration from previous studies. Therefore, transverse stiffeners were more effective than longitudinal ones. This study highlights the importance of stiffener orientation and geometry in the structural optimization of thin steel plates.

The climate crisis represents one of the greatest contemporary global challenges, requiring actions to mitigate its impacts and sustainable solutions to meet the growing demands for clean energy and coastal protection. Therefore, the study of devices such as the submerged plate (SP), which simultaneously acts as a breakwater (BW) and wave energy converter (WEC), is especially relevant. In this context, the present numerical study compares the efficiency of an SP device under regular waves across different geometric configurations considering inclination angles. To achieve this, a horizontal SP was adopted as a reference. Its thickness and total material volume were kept constant while ten alternative geometries, each with a different inclination for the SP, were proposed and investigated. The computational domain was modeled as a full-scale regular wave channel with each SP positioned below the free surface. The volume of fluid (VOF) multiphase model was employed to represent the interaction between water and air. The finite volume method (FVM) was applied to solve the transport equations for volume fraction, momentum, and mass. The SP’s efficiency as a BW was evaluated by assessing the free surface elevation upstream and downstream of the SP, while its efficiency as a WEC was measured by evaluating the axial velocity below the SP. Results indicated that the efficiency of the SP can vary significantly depending on its inclination, with the optimal case at θ = 15° showing improvements of 11.95% and 16.59%, respectively, as BW and WEC.

The aim of this work is to examine, from the perspective of Constructal Design, the influence of the width (W_pcm ) of a reservoir filled with PCM (phase change material) on the cooling performance of a Li-ion battery cell under discharge rates of 3C and 5C. The problem is considered two-dimensional and transient. The mathematical model is multiphase, with different characteristics for the solid domain (battery cell) and the fluid domain (PCM reservoir), based on the mass, momentum and energy balance equations. The finite volume method is used to solve the problem numerically, and the grid meshes used in the spatial discretization are subjected to uncertainty analysis. The results show that the use of the PCM reservoir contributes significantly to the cooling of the battery. When the battery discharge occurs at a rate of 5C, there is a 13.1°C reduction in the maximum temperature of the battery (T_max ).

A hyperparameter-optimized Kriging surrogate model was developed for the structural collapse behavior framework presented in this paper. The assessment is conducted on a stiffened panel subject to axial load and lateral pressure, typical of the deck structure of a bulk carrier ship. This behavior is characterized using nonlinear finite element analysis to determine the collapse response. The surrogate model’s hyperparameters were optimized using a Genetic Algorithm to achieve the best performance, and the trained framework can predict ultimate strength. By following this approach, the problem can be reformulated as a multi-objective optimization task. This framework involves associating the Kriging surrogate model with a multi-objective evolutionary optimization algorithm based on Genetic Algorithms to balance the trade-off between the weight and ultimate strength of the stiffened panel. The results confirm the applicability of the Kriging surrogate framework to predict the ultimate strength and assess the collapse analysis of the stiffened panels, ensuring accuracy through GA-based hyperparameter optimization.