Jhon Goulart - Profile on Academia.edu (original) (raw)
Papers by Jhon Goulart
International Journal of Heat and Mass Transfer, Oct 1, 2018
Present numerical study performs a geometrical optimization by means of Constructal Design and Ex... more Present numerical study performs a geometrical optimization by means of Constructal Design and Exhaustive Search of two alternated rectangular heated bodies mounted in channel surfaces subjected to steady, two-dimensional, incompressible, laminar and forced convective air cooled flows. The problem has two purposes, maximize the heat transfer rate between the bodies and surrounding flow (q) and minimize pressure drop (DP) in the channel, i.e., a multi-objective problem. The system is subjected to five constraints, but only two are evaluated here: area fractions of first and second bodies (/ 1 and / 2 ). The problem has two degrees of freedom: ratio between the height and length of upward and downward bodies (H 1 /L 1 and H 2 /L 2 ) placed in lower and upper surfaces of the channel, respectively. The influence of fraction areas on the system performance is also investigated. All simulations are performed with constant Reynolds and Prandtl numbers, Re H = 100 and Pr = 0.71. As expected, highest intrusion and areas of the bodies were benefical for heat exchange, while the opposite was noticed for pressure drop. For multiobjective optimization, intermediate optimal shapes with assimetric sizes were achieved. The best multiobjective performance is reached for the upward body higher than the downstream one (H 1 /L 1 > H 2 /L 2 ).
Engenharia térmica, Dec 31, 2011
The study of turbulence characteristics in compound channels is still focus of attention. A lot o... more The study of turbulence characteristics in compound channels is still focus of attention. A lot of experimental results have been produced. Main results have revealed a mixing layer formation between main subchannel and the gap region, implying the flow might be ruled by local scales. The outcomes have pointed to the instabilities of mixing layer are responsible for large structures formation between main channel and narrow gap. Furthermore, the periodical behavior of these structures seems to be ruled by mean mixing layer characteristics, as velocity difference, velocity of convection and mixing layer thickness. By using ANSYS-CFX-12, with unsteady Reynolds Average Navier-Stokes and as turbulence model Spalart-Allmaras (SA), a compound channel was studied. Numerical results predicted velocity profile with high vorticity peaks and flow instabilities starting at L/D h = 15.
International Journal of Heat and Fluid Flow, Oct 1, 2016
A three-dimensional unsteady simulation was carried out to predict the main features of the turbu... more A three-dimensional unsteady simulation was carried out to predict the main features of the turbulent flow inside a closed channel connected to a lateral slot. The incompressible turbulent flow was modelled using a hybrid Detached Eddy Simulation (DES), that uses an LES/URANS approach to predict the turbulence. The calculations were performed using ANSYS ® CFX. In this work the main channel has a size of 180 mm x 136.20 mm. The small subchannel is characterized by its deepness, p = 77 mm and width, d = 10 mm. The Reynolds number, based on the hydraulic-diameter, D h , the bulk velocity, and the kinematic viscosity, , in the main channel was Re = 2.25 × 10 5 . Inside the small slot the velocity distribution was found to depart from the law of the wall and the normal Reynolds stresses, '' uu and '' vv, were found to dominate the mixing process. Velocity time-traces extracted at locations as far as y/p = 1.125 inside the gap evidenced the presence of large eddies travelling inside the small channel. It was shown that periodic streamwise boundary conditions can be applied to this problem, and good results were obtained by using a channel length that was approximately twice the wavelength of the experimentally observed coherent structures. The results were found to be in fair agreement with the results presented in Meyer and Rehme (1994), though a certain lack of information on turbulence in single channels connected to a gap still remains.
Formulação RANS Aplicada ao Escoamento Monofásico e Bifásico em uma Bomba Centrifuga
Revista Interdisciplinar de Pesquisa em Engenharia, Sep 2, 2020
In this work numerical simulation of single and bi-phase flows are carried out in a centrifugal p... more In this work numerical simulation of single and bi-phase flows are carried out in a centrifugal pump. The main goal is to simulate both head and the efficiency curves for different angular velocities face single and two phase flows. To achieve such goals commercial Ansys CFX platform was employed. The physical model was discretized into finite volumes and the turbulence model employed was k-I‰ SST along with Rayleigh-Plesset to model the bubble increasing for cavitation modelling. At the first stage both head and the efficiency curves were simulated under single phase flow for three different angular velocities, 1250, 1500 and 2000 RPM. In sequence bi-phase flow was prescribed at the pump inlet to analyse the same head and efficiency curves under the light of the vapour/liquid mixture. During the simulation only liquid and/or vapour water, at 25°C were employed. As the main results the vapour-water was seen to increase as the leading to a head decrease in comparison with the single phase flow, does not matter which the angular velocity prescribed. The required NPSH was then computed and compared with the based on the open literature formula, through the Thoma factor, s. Despite of the certain scattering of the data the Thoma factor was found to be fitted by exponential curve as s=C nq4/3, being C the constant and nq the specific pump rotation.
Revista Facultad De Ingenieria-universidad De Antioquia, Oct 24, 2013
The hot-wire anemometry technique was employed to study the velocity distribution and dynamic cha... more The hot-wire anemometry technique was employed to study the velocity distribution and dynamic characteristics of the flow in two types of closed compound channels. The compound channels were built using two rectangular tubes attached to the walls of a wind channel separated by a distance d. In this configuration, a narrow gap is connected to a main subchannel. The results revealed an interesting flow that was quite similar to a mixing layer. All axial velocity profiles presented turning points at the main subchannel/ narrow gap interface. By using quantities from the mean flow velocity distribution, the flow could be described by a hyperbolic tangent function, and a Strouhal number was suggested as well. Regardless of the channel type, the dimensionless frequency was almost constant, resulting in a Strouhal number of approximately 0.10.
This paper presents the experimental study of velocity distribution and pressure fluctuations of ... more This paper presents the experimental study of velocity distribution and pressure fluctuations of the cross flow in a simulated tube bank, with square arrangement and a pitch to diameter ratio of 1.26. Measurements were performed with hot wires and a pressure transducer. Behavior of fluctuating quantities is described by means of dimensionless autospectral density functions and their interdependence is discussed. Results show the flow redistribution after the baffles and a dimensionless characteristic frequency in form of a Strouhal number Str = 0.33.
Hot wire anemometry and pressure transducer techniques applied to the detection of the bistable flow over a pair of circular cylinders
Revista Interdisciplinar de Pesquisa em Engenharia, 2019
In this paper the pressure field and its fluctuation around circular cylinders arranged in pairs ... more In this paper the pressure field and its fluctuation around circular cylinders arranged in pairs will be measured, as well as the wake characteristics behind each cylinder. The experimental investigation is carried out in an aerodynamic channel with turbulence intensity of free stream less than 3%. The pressure and its fluctuation were gathered through a pressure transducer whereas the velocity fields were measured by using single hot-wire probes. Mathematical tools were employed to identify flow patterns in the velocity and pressure time-traces. During the experimental campaign three p/d-ratio were tested, p/d = 1.26, 2.00 and 3.00, for a constant Reynolds number, ReD = 1.78 x 104, based on the circular cylinder diameter, D, the free stream velocity U∞, and the kinematic viscosity of the fluid, ν. Through the pressure measurements it was identified that the mean average pressure distribution around the cylinders departs from the one that takes place in a single cylinder as the p/d-ratio decreases. As regards the dynamic of the flow two distinguished behaviors were observed: for intermediated p/d-ratio (2 and 3), the Strouhal number was found slighted superior to 0.21, on the other hand, for the lowest p/d-ratio, the pressure spectrum did not present important peaks. Time-frequency tools were also employed to analyze the dynamic behavior of the flow velocity behind the circular cylinders showing a kind of intermittent process in the vortex shedding when the p/d-ratio decreases.
Sensitivity Analysis of Discrete Wavelet (DWT) Based Damage Localization on a Beam-Like Structure
Proceedings of the XIX International Symposium on Dynamic Problems of Mechanics
A Numerical Study of Aerodynamic Coefficients of a Ground Vehicle
Revista Interdisciplinar de Pesquisa em Engenharia, Dec 31, 2020
O proposito deste trabalho e apresentar um estudo numerico de um canal bidimensional com duas ale... more O proposito deste trabalho e apresentar um estudo numerico de um canal bidimensional com duas aletas retangulares submetido a um escoamento no regime laminar com transferencia de calor por conveccao forcada avaliando a geometria das aletas atraves do metodo Design Construtal. Os objetivos principais sao maximizar a taxa de transferencia de calor e ao mesmo tempo minimizar a diferenca de pressoes entre a entrada e saida do canal para diferentes dimensoes das duas aletas do canal, considerando os mesmos numeros de Reynolds (ReH= 100) e Prandtl (Pr = 0,71). O problema e submetido a tres restricoes dadas pelas areas do canal, aletas e area maxima de ocupacao de cada aleta. O sistema ainda possui tres graus de liberdade dados pela razao entre altura e comprimento do canal, que e mantida fixa H/L = 0,0625, a razao entre altura e comprimento da aleta frontal (H3/L3) situada na superficie inferior do canal e a razao entre altura e comprimento da aleta posterior (H4/L4) localizada na superfi...
Optimización topológica de sólidos en calor y transferencia de masa utilizando los elementos de contorno
Revista Facultad De Ingenieria-universidad De Antioquia, 2012
The objetive of this work is to present the implementation of topologicalshape sensitivity formul... more The objetive of this work is to present the implementation of topologicalshape sensitivity formulation in a BEM analysis for simultaneous heat and mass transfer optimization problems. The proposed approach uses a topological derivative in order to estimate the sensitivity to create a hole in the domain of the problem. Thus, it is evaluated at internal points, and the ones showine the lowest values are used to remove material by opening a circular cavity. As the iterative process evolves, the original domain has holes progressively punched out until a given stop criteria is achieved. Since the sensitivities for each of the differential equations are different, a penalization-type approach has been used to weight the sensitives associated to each problem, This allows the imposition of district penalization factor for each problem, according to especified priorities. The result obtained showed good agreement with solutions avaliable in the literature.El objetivo de este trabajo es presentar la aplicación de una formulación para el análisis de sensibilidad de forma y topologia utilizando elemetos de contorno en problemas de optimización involucrando transferencia simultanea de calor y masa. El enfoque propuesto usa la derivada topológica para estimar la sensibilidad a criar un agujero en el dominio de definición del problema. De este modo, la misma se evalua en puntos internos y aquellos que presentan los valores más bajos se utilizan para eliminar material mediante la apertura de una cavidad circular. A medida que el proceso iterativo evoluciona, el dominio se modifica progresivamente con la incorporación de más agujeros hasta que se alcanza un criterio de parada determinado. Puesto que las sensibilidades de cada una de las ecuaciones diferenciales son diferentes, un enfoque tipo penalización ha sido utilizado para ponderar las sensibilidades asociadas a cada problema. Esto permite la imposición de factores de penalización distintos para cada problema, de acurdo a prioridades específicas. Los resultados obtenidos mostraron una buena concordancia con soluciones disponibles em la literatura
Engineering Optimization, 2018
This work investigates the optimization of elasticity problems using the boundary element method ... more This work investigates the optimization of elasticity problems using the boundary element method (BEM) as a numerical solver. A topological shape sensitivity approach is used to select the points showing the lowest sensitivities. As the iterative process evolves, the original domain has portions of material progressively removed in the less efficient areas until a given stop criterion is achieved. Two benchmark tests are investigated to demonstrate the influence of the boundary conditions on the final topology. Following this, a suspension trailing arm is optimized and a new design is proposed as an alternative to commercially available methods. A postprocedure of smoothing using Bézier curves was employed for the final topology of the trailing arm. This process allowed the external irregular shapes to be overcome. The BEM coupled with the topological derivative was shown to be an alternative to traditional optimization techniques using the finite element method. The present methodology was shown to be efficient for delivering optimal topologies with few iterations. All routines used were written in open code.
Resumo. O propósito deste trabalho é investigar numérica e experimentalmente a distribuição de ve... more Resumo. O propósito deste trabalho é investigar numérica e experimentalmente a distribuição de velocidade, bem como a estrutura da turbulência em um canal composto formado por um canal principal retangular e duas placas paralelas conectadas a uma das paredes laterais, de forma que o comprimento total, L, pudesse ser variado. Para tanto foi utilizada a anemometria de fio quente, como técnica experimental e o software CFX®, versão 5.6, na simulação do escoamento, utilizando os modelos de turbulência k-ε e Simulação de Grandes Escalas, SGE. Os dados, tanto numéricos como experimentais, mostraram um escoamento altamente cisalhante na fronteira entre os dois canais com estruturas coerentes carregadas pelo escoamento médio. Palavras chave:simulação numérica, canais compostos, escoamento cisalhante, estruturas coerentes. De maneira geral os canais classificados como compostos são caracterizados pela presença de um canal principal e um ou mais canais secundários, sendo o uso destas estruturas bastante vasto na dentro engenharia, começando em trocadores de calor, passando pelo interior de reatores e até mesmo em canais de água, principalmente canais artificiais. No entanto as investigações sobre o escoamento turbulento neste tipo de canal mostram características peculiares em relação à distribuição das tensões turbulentas e o coeficiente de transferência local de calor na fronteira entre dois canais. Medições experimentais realizadas por Möller, 1991, em um feixe de barras, com apenas uma linha, mostraram altos valores de intensidade de turbulência, para as componentes axial e azimutal de velocidade, na região das fendas e uma forte dependência entre o aumento destas quantidades e o decrescimento da distancia entre os tubos. As flutuações das diferentes componentes de velocidade mostraram um comportamento quasi-periódico próximo as fendas, tal qual como identificado por , que sugeria que estas pulsações do escoamento eram responsáveis pelo aumento das intensidades turbulentas junto na fenda. Meyer e Rheme, 1995, investigaram, experimentalmente, a distribuição de velocidade e a características do escoamento turbulento em canais retangulares com slots na parede lateral, para uma faixa de número de Reynolds de 2300 até 10 5 . Para todas as configurações, a seção de teste foi assumida longa o suficiente para o desenvolvimento do escoamento, a relação entre o comprimento das seções e o diâmetro hidráulico, L/D h , variou entre 45 e 94. Neste trabalho, além das diferentes configurações das seções de teste, também foi analisada a influência da viscosidade e dos parâmetros geométricos do slot, como largura "g" e profundidade "d", na formação dos campos de velocidade e no comportamento dinâmico da turbulência dentro da fenda. De forma geral os campos de velocidade mostram-se qualitativamente muito semelhantes com o aumento da viscosidade, enquanto os auto-espectros de flutuação de velocidade mostraram picos, mesmo para valores de Reynolds tão baixos quanto Re=150, indicando a presença destas estruturas coerentes, que segundo o autor estão presentes em qualquer slot longitudinal onde a profundidade é maior ou igual a duas vezes a largura da fenda, d>= 2g. O comprimento de onda destas pulsações do escoamento mostrou-se ser constante para uma dada geometria e revelou-se uma função exclusivamente da geometria. Biemüller et al. 1996, investigou numericamente as características do escoamento turbulento em dois canais retangulares conectados por uma fenda, junto a parede superior, usando Simulação de Grandes Escalas, SGE. A altura e largura do canal eram, respectivamente, 180 e 331,6 mm e seu comprimento 504 mm. A fenda que conecta os dois canais principais possui altura, g, e largura, d, de 10,20 e 40,6 mm, respectivamente, portanto uma relação g/d=4. No domínio computacional a seção transversal foi considerada infinita, com condições de contorno periódicas nesta
Resumo. O propósito deste trabalho numérico/experimental é investigar o desenvolvimento e as cara... more Resumo. O propósito deste trabalho numérico/experimental é investigar o desenvolvimento e as características do escoamento ao longo de feixe de tubos com placas defletoras. O banco de tubos possui duas linhas, com razão de espaçamento P/D=1,26 e comprimento de 450 mm, onde existem duas placas defletoras direcionando o escoamento principal e criando uma entrada assimétrica no feixe de tubos. O número de Reynolds foi calculado utilizando-se o diâmetro externo do tubo e a velocidade de entrada, 3.32 x 10 4 . A distribuição de velocidade foi obtida experimentalmente empregando anemometria de fio quente e para a análise numérica utilizou-se o programa CFX versão 5.6. A análise numérica foi feita baseada na Simulação de Grandes Escalas (Large Eddy Simulation -LES), com o modelo de Smagorinsky e nas Equações de Navier-Stokes médias de Reynolds (Reynolds Averaged Navier-Stokes Equations-RANS), com o modelo κ-ε. O campo de pressões médias na parede lateral do banco também foi analisado. Os resultados numéricos e experimentais apresentaram boa concordância para os campos médios de velocidades e pressões. Palavras chave: banco de tubos, placas defletoras, turbulência experimental, simulação de grandes escalas, equações médias de Reynolds A utilização de placas defletoras em feixe de tubos é muito difundida em trocadores de calor, aumentando os níveis de turbulência do escoamento e o tempo de contato do fluido refrigerante e a superfície aquecida dos tubos. Os vórtices gerados pela turbulência influenciam a camada limite térmica dos tubos, onde o calor é trocado basicamente por condução, tornando a troca de calor mais eficiente. No entanto, a maioria dos estudos em bancos de tubos considera um escoamento incidindo uniformemente sobre os tubos, sem qualquer tipo de análise dos efeitos causados pela utilização de placas defletoras, transformando-se assim em idealizações pouco reais, Yeung e Weaver (1983). Já em reatores nucleares, estes utilizam, em geral, feixes de barras cilíndricas como elementos combustível., onde cada barra é constituída de material físsil propriamente revestido. O calor gerado pelo processo de fissão nuclear e é transferido ao fluido, que circula axialmente ao feixe de barras, sendo a otimização destas taxas é função tanto das propriedades físicas do fluido quanto das características do escoamento e do feixe de tubos (arranjo e relações de espaçamento). A tentativa de aumentar as taxas de transferência de calor em trocadores de calor, através do aumento da velocidade do fluido ou a redução das relações de espaçamento entre tubos, pode levar ao surgimento de cargas dinâmicas, induzindo vibrações, que são apontadas como uma das principais causas de falhas nos componentes de trocadores de calor, . Em , encontra-se um estudo experimental do efeito produzido pela presença de um defletor em um feixe de tubos. O escoamento turbulento era desviado pelo defletor atingindo o banco de tubos com um ângulo de incidência diferente de 90º. Os resultados de pressões e flutuações de pressão medidas em torno da parede de um tubo instrumentado no interior do banco de tubos, apresentaram maiores valores do que no escoamento transversal. Apareceram picos adicionais no espectro de flutuações de pressão na parede, que não puderam ser associados a nenhum dos efeitos do escoamento transversal puro nem aos efeitos produzidos somente pelo defletor. Portanto, os resultados apresentados não eram conclusivos, motivando estudos em separado, analisando o efeito causado por placas defletoras, , e um estudo experimental do escoamento através de banco de tubos inclinados, . O escoamento incidindo sobre placas defletoras, sem a utilização de tubos, foi analisado numérica e experimentalmente por . Os autores observaram o processo de separação da camada limite e a indução de recirculações do escoamento nas extremidades dos defletores, podendo significar uma importante fonte de
European Journal of Mechanics - B/Fluids, 2020
The aim of this work is to perform a numerical simulation of the turbulent flow in an eccentric c... more The aim of this work is to perform a numerical simulation of the turbulent flow in an eccentric channel for a Reynolds number Re Dh = 7300. The Reynolds number is based on the bulk velocity, U Bulk , the hydraulic-diameter, D h , and the kinematic viscosity, ν. To achieve this goal, a hybrid RANS/LES turbulence model called DES-SST is used. In this formulation, special functions are computed to convert the model from RANS close to the walls to LES in more remote regions. Besides the Reynolds number, the main dimensionless parameter related to the geometry involves the narrow gap between the outer and inner walls of the pipes and their diameters, D and d, respectively. These geometric parameters are related to the eccentricity, e, and the d/D ratio. Both of these parameters were kept constant at 0.80 and 0.50, respectively, throughout the work, as the channel's length, L = 1500 mm. The numerical results are compared with experimental outcomes for a water channel with the same Reynolds number using PIV measurements. The hybrid scheme was able to capture the onset of gap instability, short after the channel's inlet. Furthermore, the mass flow distribution along the channel and the flow velocity patterns were also successfully predicted by the numerical code. The Strouhal number was found to be in fair agreement with the experimental result. The large-scale structures were found to spread over the whole cross-section. The main frequency produced by the oscillatory motion in the tight gap was seen to be twice as high as that found in the lateral subchannel.
Uncertainty Modeling: Fundamental Concepts and Models
This chapter presents an overview of computational models and formulations, a description of some... more This chapter presents an overview of computational models and formulations, a description of some error estimators in Boundary Element Methods (BEM) and in Finite Element Methods (FEM), and some perspectives of the use of these error estimators in Bayesian approaches for Model Validation.
Otimização Geométrica De Escoamentos Com Convecção Forçada Sobre Um Arranjo De Quatro Cilindros
O presente estudo consiste na avaliacao numerica de um arranjo formado por quatro cilindros subme... more O presente estudo consiste na avaliacao numerica de um arranjo formado por quatro cilindros submetidos a um escoamento transiente, bidimensional, incompressivel, laminar e com conveccao forcada. A avaliacao geometrica e realizada atraves do metodo Design Construtal. O problema possui uma restricao dada pela soma da area dos cilindros e tres graus de liberdade: ST1/D (razao entre o passo transversal dos cilindros frontais e o diâmetro dos cilindros), ST2/D (razao entre o passo transversal dos cilindros posteriores e o diâmetro dos cilindros) e SL/D (razao entre o passo longitudinal dos cilindros frontais e posteriores e o diâmetro dos cilindros). Para todas as simulacoes sao considerados numeros de Reynolds e Prandtl constantes, ReD = 100 e Pr = 0.71. As equacoes de conservacao de massa, quantidade de movimento e energia sao resolvidas atraves do Metodo dos Volumes Finitos (FVM). O principal objetivo e avaliar o efeito dos graus de liberdade sobre o coeficiente de arrasto (C D) e o n...
Otimização Geométrica De Escoamentos Com Convecção Forçada Sobre Um Arranjo Triangular De Corpos Rombudos Quadrados
O presente estudo consiste na avaliacao numerica de um arranjo triangular de corpos rombudos subm... more O presente estudo consiste na avaliacao numerica de um arranjo triangular de corpos rombudos submetidos a um escoamento transiente, bidimensional, incompressivel, laminar e com conveccao forcada. A avaliacao geometrica e realizada atraves do metodo Design Construtal. O problema possui uma restricao dada pela soma da area dos corpos rombudos e dois graus de liberdade: ST/D (razao da distância entre o centro dos corpos rombudos posteriores e a dimensao de suas arestas), SL/D (razao da distância longitudinal entre os centros dos corpos rombudos, frontal e posteriores, e a dimensao de suas arestas). Para todas as simulacoes sao considerados numeros de Reynolds e Prandtl constantes, ReD=100 e Pr = 0.71. As equacoes de conservacao de massa, quantidade de movimento e energia sao resolvidas atraves do Metodo dos Volumes Finitos (FVM). O principal objetivo e avaliar o efeito dos graus de liberdade sobre o coeficiente de arrasto (CD) e o numero de Nusselt (NuD) entre os corpos rombudos e o es...
Constructal Design Applied to a Channel with Triangular Fins Submitted to Forced Convection
Defect and Diffusion Forum, 2017
The purpose of this work is to present a numerical study of a two-dimensional channel with two tr... more The purpose of this work is to present a numerical study of a two-dimensional channel with two triangular fins submitted to a laminar flow with forced convection heat transfer, evaluating the geometry of the first fin through the Constructal Design method. The main objectives are to maximize the heat transfer rate and minimize the pressure difference between the inlet and outlet flow of the channel for different dimensions of the first channel fin, considering the same Reynolds (ReH = 100) and Prandtl numbers (Pr = 0.71). The problem is subjected to three constraints given by the channel area, fin area and maximum occupancy area of each fin. The system has three degrees of freedom. The first is given by the ratio between height and length of the channel, which is kept fixed, H/L = 0.0625. The other two are the ratio between height and width of the upstream fin base (H3/L3) positioned on the lower surface of the channel, and the ratio between height and width of the downstream fin (H4/L4) positioned on the upper surface of the channel, which is also kept fixed, H4/L4 = 1.11. The problem is simulated for three different values of the fraction area of upstream fin (φ1 = 0.1, 0.2 and 0.3). For the numerical approach of the problem, the conservation equations of mass, momentum and energy are solved using the finite volume method (MVF). The results showed that a ratio of φ1 = 0.2 is the one that best meets the proposed multi-objective. It was also observed that φ1 = 0.1 led to a better fluid dynamics performance with a ratio between the best and the worst performance for fluid dynamics case of 25.2 times. For φ1 = 0.3, the best thermal performance is achieved, where the optimal case has a performance 65.75% higher than that reached for the worst case.
Geometric Evaluation of Forced Convective Flows across an Arrangement of Four Circular Cylinders
Defect and Diffusion Forum, 2017
The present study consists in a numerical evaluation of an arrangement formed by four cylinders s... more The present study consists in a numerical evaluation of an arrangement formed by four cylinders submitted to an unsteady, two-dimensional, incompressible, laminar and forced convective flow. The geometric evaluation is performed through the Constructal Design method. The problem has two restrictions given by the sum of the area of the cylinders and one occupation area and has three degrees of freedom: ST1/D (the ratio between the transverse pitch of the frontal cylinders and the diameter of the cylinders), ST2/D (the ratio between the transverse pitch of the posterior cylinders and the diameter of the cylinders) and SL/D (ratio between the longitudinal pitch of the frontal and posterior cylinders and the diameter of the cylinders). For all simulations the Reynolds number is kept constant, ReD = 100, and two different Prandtl numbers of Pr = 0.71 and 5.83 are considered, which simulates respectively the use of air and water as a fluid. The conservation equations of mass, momentum and energy are solved with the Finite Volume Method (FVM). The main objective is to evaluate the effect of the degrees of freedom on the drag coefficient (CD) and the Nusselt number (NuD) between the cylinders and the surrounding flow, as well as the optimal ST2/D values for three ratios of ST1/D = 1.5, 3.0 and 4.0, these results being obtained for ratios of SL/D = 1.5 and 4.0. Results showed that the ratio changes of ST1/D and ST2/D have a great influence on the drag coefficients and on the Nusselt number of the arrangement formed by the four cylinders, as well as on the geometries leading to the best fluid dynamics and thermal performance.
International Journal of Heat and Mass Transfer, Oct 1, 2018
Present numerical study performs a geometrical optimization by means of Constructal Design and Ex... more Present numerical study performs a geometrical optimization by means of Constructal Design and Exhaustive Search of two alternated rectangular heated bodies mounted in channel surfaces subjected to steady, two-dimensional, incompressible, laminar and forced convective air cooled flows. The problem has two purposes, maximize the heat transfer rate between the bodies and surrounding flow (q) and minimize pressure drop (DP) in the channel, i.e., a multi-objective problem. The system is subjected to five constraints, but only two are evaluated here: area fractions of first and second bodies (/ 1 and / 2 ). The problem has two degrees of freedom: ratio between the height and length of upward and downward bodies (H 1 /L 1 and H 2 /L 2 ) placed in lower and upper surfaces of the channel, respectively. The influence of fraction areas on the system performance is also investigated. All simulations are performed with constant Reynolds and Prandtl numbers, Re H = 100 and Pr = 0.71. As expected, highest intrusion and areas of the bodies were benefical for heat exchange, while the opposite was noticed for pressure drop. For multiobjective optimization, intermediate optimal shapes with assimetric sizes were achieved. The best multiobjective performance is reached for the upward body higher than the downstream one (H 1 /L 1 > H 2 /L 2 ).
Engenharia térmica, Dec 31, 2011
The study of turbulence characteristics in compound channels is still focus of attention. A lot o... more The study of turbulence characteristics in compound channels is still focus of attention. A lot of experimental results have been produced. Main results have revealed a mixing layer formation between main subchannel and the gap region, implying the flow might be ruled by local scales. The outcomes have pointed to the instabilities of mixing layer are responsible for large structures formation between main channel and narrow gap. Furthermore, the periodical behavior of these structures seems to be ruled by mean mixing layer characteristics, as velocity difference, velocity of convection and mixing layer thickness. By using ANSYS-CFX-12, with unsteady Reynolds Average Navier-Stokes and as turbulence model Spalart-Allmaras (SA), a compound channel was studied. Numerical results predicted velocity profile with high vorticity peaks and flow instabilities starting at L/D h = 15.
International Journal of Heat and Fluid Flow, Oct 1, 2016
A three-dimensional unsteady simulation was carried out to predict the main features of the turbu... more A three-dimensional unsteady simulation was carried out to predict the main features of the turbulent flow inside a closed channel connected to a lateral slot. The incompressible turbulent flow was modelled using a hybrid Detached Eddy Simulation (DES), that uses an LES/URANS approach to predict the turbulence. The calculations were performed using ANSYS ® CFX. In this work the main channel has a size of 180 mm x 136.20 mm. The small subchannel is characterized by its deepness, p = 77 mm and width, d = 10 mm. The Reynolds number, based on the hydraulic-diameter, D h , the bulk velocity, and the kinematic viscosity, , in the main channel was Re = 2.25 × 10 5 . Inside the small slot the velocity distribution was found to depart from the law of the wall and the normal Reynolds stresses, '' uu and '' vv, were found to dominate the mixing process. Velocity time-traces extracted at locations as far as y/p = 1.125 inside the gap evidenced the presence of large eddies travelling inside the small channel. It was shown that periodic streamwise boundary conditions can be applied to this problem, and good results were obtained by using a channel length that was approximately twice the wavelength of the experimentally observed coherent structures. The results were found to be in fair agreement with the results presented in Meyer and Rehme (1994), though a certain lack of information on turbulence in single channels connected to a gap still remains.
Formulação RANS Aplicada ao Escoamento Monofásico e Bifásico em uma Bomba Centrifuga
Revista Interdisciplinar de Pesquisa em Engenharia, Sep 2, 2020
In this work numerical simulation of single and bi-phase flows are carried out in a centrifugal p... more In this work numerical simulation of single and bi-phase flows are carried out in a centrifugal pump. The main goal is to simulate both head and the efficiency curves for different angular velocities face single and two phase flows. To achieve such goals commercial Ansys CFX platform was employed. The physical model was discretized into finite volumes and the turbulence model employed was k-I‰ SST along with Rayleigh-Plesset to model the bubble increasing for cavitation modelling. At the first stage both head and the efficiency curves were simulated under single phase flow for three different angular velocities, 1250, 1500 and 2000 RPM. In sequence bi-phase flow was prescribed at the pump inlet to analyse the same head and efficiency curves under the light of the vapour/liquid mixture. During the simulation only liquid and/or vapour water, at 25°C were employed. As the main results the vapour-water was seen to increase as the leading to a head decrease in comparison with the single phase flow, does not matter which the angular velocity prescribed. The required NPSH was then computed and compared with the based on the open literature formula, through the Thoma factor, s. Despite of the certain scattering of the data the Thoma factor was found to be fitted by exponential curve as s=C nq4/3, being C the constant and nq the specific pump rotation.
Revista Facultad De Ingenieria-universidad De Antioquia, Oct 24, 2013
The hot-wire anemometry technique was employed to study the velocity distribution and dynamic cha... more The hot-wire anemometry technique was employed to study the velocity distribution and dynamic characteristics of the flow in two types of closed compound channels. The compound channels were built using two rectangular tubes attached to the walls of a wind channel separated by a distance d. In this configuration, a narrow gap is connected to a main subchannel. The results revealed an interesting flow that was quite similar to a mixing layer. All axial velocity profiles presented turning points at the main subchannel/ narrow gap interface. By using quantities from the mean flow velocity distribution, the flow could be described by a hyperbolic tangent function, and a Strouhal number was suggested as well. Regardless of the channel type, the dimensionless frequency was almost constant, resulting in a Strouhal number of approximately 0.10.
This paper presents the experimental study of velocity distribution and pressure fluctuations of ... more This paper presents the experimental study of velocity distribution and pressure fluctuations of the cross flow in a simulated tube bank, with square arrangement and a pitch to diameter ratio of 1.26. Measurements were performed with hot wires and a pressure transducer. Behavior of fluctuating quantities is described by means of dimensionless autospectral density functions and their interdependence is discussed. Results show the flow redistribution after the baffles and a dimensionless characteristic frequency in form of a Strouhal number Str = 0.33.
Hot wire anemometry and pressure transducer techniques applied to the detection of the bistable flow over a pair of circular cylinders
Revista Interdisciplinar de Pesquisa em Engenharia, 2019
In this paper the pressure field and its fluctuation around circular cylinders arranged in pairs ... more In this paper the pressure field and its fluctuation around circular cylinders arranged in pairs will be measured, as well as the wake characteristics behind each cylinder. The experimental investigation is carried out in an aerodynamic channel with turbulence intensity of free stream less than 3%. The pressure and its fluctuation were gathered through a pressure transducer whereas the velocity fields were measured by using single hot-wire probes. Mathematical tools were employed to identify flow patterns in the velocity and pressure time-traces. During the experimental campaign three p/d-ratio were tested, p/d = 1.26, 2.00 and 3.00, for a constant Reynolds number, ReD = 1.78 x 104, based on the circular cylinder diameter, D, the free stream velocity U∞, and the kinematic viscosity of the fluid, ν. Through the pressure measurements it was identified that the mean average pressure distribution around the cylinders departs from the one that takes place in a single cylinder as the p/d-ratio decreases. As regards the dynamic of the flow two distinguished behaviors were observed: for intermediated p/d-ratio (2 and 3), the Strouhal number was found slighted superior to 0.21, on the other hand, for the lowest p/d-ratio, the pressure spectrum did not present important peaks. Time-frequency tools were also employed to analyze the dynamic behavior of the flow velocity behind the circular cylinders showing a kind of intermittent process in the vortex shedding when the p/d-ratio decreases.
Sensitivity Analysis of Discrete Wavelet (DWT) Based Damage Localization on a Beam-Like Structure
Proceedings of the XIX International Symposium on Dynamic Problems of Mechanics
A Numerical Study of Aerodynamic Coefficients of a Ground Vehicle
Revista Interdisciplinar de Pesquisa em Engenharia, Dec 31, 2020
O proposito deste trabalho e apresentar um estudo numerico de um canal bidimensional com duas ale... more O proposito deste trabalho e apresentar um estudo numerico de um canal bidimensional com duas aletas retangulares submetido a um escoamento no regime laminar com transferencia de calor por conveccao forcada avaliando a geometria das aletas atraves do metodo Design Construtal. Os objetivos principais sao maximizar a taxa de transferencia de calor e ao mesmo tempo minimizar a diferenca de pressoes entre a entrada e saida do canal para diferentes dimensoes das duas aletas do canal, considerando os mesmos numeros de Reynolds (ReH= 100) e Prandtl (Pr = 0,71). O problema e submetido a tres restricoes dadas pelas areas do canal, aletas e area maxima de ocupacao de cada aleta. O sistema ainda possui tres graus de liberdade dados pela razao entre altura e comprimento do canal, que e mantida fixa H/L = 0,0625, a razao entre altura e comprimento da aleta frontal (H3/L3) situada na superficie inferior do canal e a razao entre altura e comprimento da aleta posterior (H4/L4) localizada na superfi...
Optimización topológica de sólidos en calor y transferencia de masa utilizando los elementos de contorno
Revista Facultad De Ingenieria-universidad De Antioquia, 2012
The objetive of this work is to present the implementation of topologicalshape sensitivity formul... more The objetive of this work is to present the implementation of topologicalshape sensitivity formulation in a BEM analysis for simultaneous heat and mass transfer optimization problems. The proposed approach uses a topological derivative in order to estimate the sensitivity to create a hole in the domain of the problem. Thus, it is evaluated at internal points, and the ones showine the lowest values are used to remove material by opening a circular cavity. As the iterative process evolves, the original domain has holes progressively punched out until a given stop criteria is achieved. Since the sensitivities for each of the differential equations are different, a penalization-type approach has been used to weight the sensitives associated to each problem, This allows the imposition of district penalization factor for each problem, according to especified priorities. The result obtained showed good agreement with solutions avaliable in the literature.El objetivo de este trabajo es presentar la aplicación de una formulación para el análisis de sensibilidad de forma y topologia utilizando elemetos de contorno en problemas de optimización involucrando transferencia simultanea de calor y masa. El enfoque propuesto usa la derivada topológica para estimar la sensibilidad a criar un agujero en el dominio de definición del problema. De este modo, la misma se evalua en puntos internos y aquellos que presentan los valores más bajos se utilizan para eliminar material mediante la apertura de una cavidad circular. A medida que el proceso iterativo evoluciona, el dominio se modifica progresivamente con la incorporación de más agujeros hasta que se alcanza un criterio de parada determinado. Puesto que las sensibilidades de cada una de las ecuaciones diferenciales son diferentes, un enfoque tipo penalización ha sido utilizado para ponderar las sensibilidades asociadas a cada problema. Esto permite la imposición de factores de penalización distintos para cada problema, de acurdo a prioridades específicas. Los resultados obtenidos mostraron una buena concordancia con soluciones disponibles em la literatura
Engineering Optimization, 2018
This work investigates the optimization of elasticity problems using the boundary element method ... more This work investigates the optimization of elasticity problems using the boundary element method (BEM) as a numerical solver. A topological shape sensitivity approach is used to select the points showing the lowest sensitivities. As the iterative process evolves, the original domain has portions of material progressively removed in the less efficient areas until a given stop criterion is achieved. Two benchmark tests are investigated to demonstrate the influence of the boundary conditions on the final topology. Following this, a suspension trailing arm is optimized and a new design is proposed as an alternative to commercially available methods. A postprocedure of smoothing using Bézier curves was employed for the final topology of the trailing arm. This process allowed the external irregular shapes to be overcome. The BEM coupled with the topological derivative was shown to be an alternative to traditional optimization techniques using the finite element method. The present methodology was shown to be efficient for delivering optimal topologies with few iterations. All routines used were written in open code.
Resumo. O propósito deste trabalho é investigar numérica e experimentalmente a distribuição de ve... more Resumo. O propósito deste trabalho é investigar numérica e experimentalmente a distribuição de velocidade, bem como a estrutura da turbulência em um canal composto formado por um canal principal retangular e duas placas paralelas conectadas a uma das paredes laterais, de forma que o comprimento total, L, pudesse ser variado. Para tanto foi utilizada a anemometria de fio quente, como técnica experimental e o software CFX®, versão 5.6, na simulação do escoamento, utilizando os modelos de turbulência k-ε e Simulação de Grandes Escalas, SGE. Os dados, tanto numéricos como experimentais, mostraram um escoamento altamente cisalhante na fronteira entre os dois canais com estruturas coerentes carregadas pelo escoamento médio. Palavras chave:simulação numérica, canais compostos, escoamento cisalhante, estruturas coerentes. De maneira geral os canais classificados como compostos são caracterizados pela presença de um canal principal e um ou mais canais secundários, sendo o uso destas estruturas bastante vasto na dentro engenharia, começando em trocadores de calor, passando pelo interior de reatores e até mesmo em canais de água, principalmente canais artificiais. No entanto as investigações sobre o escoamento turbulento neste tipo de canal mostram características peculiares em relação à distribuição das tensões turbulentas e o coeficiente de transferência local de calor na fronteira entre dois canais. Medições experimentais realizadas por Möller, 1991, em um feixe de barras, com apenas uma linha, mostraram altos valores de intensidade de turbulência, para as componentes axial e azimutal de velocidade, na região das fendas e uma forte dependência entre o aumento destas quantidades e o decrescimento da distancia entre os tubos. As flutuações das diferentes componentes de velocidade mostraram um comportamento quasi-periódico próximo as fendas, tal qual como identificado por , que sugeria que estas pulsações do escoamento eram responsáveis pelo aumento das intensidades turbulentas junto na fenda. Meyer e Rheme, 1995, investigaram, experimentalmente, a distribuição de velocidade e a características do escoamento turbulento em canais retangulares com slots na parede lateral, para uma faixa de número de Reynolds de 2300 até 10 5 . Para todas as configurações, a seção de teste foi assumida longa o suficiente para o desenvolvimento do escoamento, a relação entre o comprimento das seções e o diâmetro hidráulico, L/D h , variou entre 45 e 94. Neste trabalho, além das diferentes configurações das seções de teste, também foi analisada a influência da viscosidade e dos parâmetros geométricos do slot, como largura "g" e profundidade "d", na formação dos campos de velocidade e no comportamento dinâmico da turbulência dentro da fenda. De forma geral os campos de velocidade mostram-se qualitativamente muito semelhantes com o aumento da viscosidade, enquanto os auto-espectros de flutuação de velocidade mostraram picos, mesmo para valores de Reynolds tão baixos quanto Re=150, indicando a presença destas estruturas coerentes, que segundo o autor estão presentes em qualquer slot longitudinal onde a profundidade é maior ou igual a duas vezes a largura da fenda, d>= 2g. O comprimento de onda destas pulsações do escoamento mostrou-se ser constante para uma dada geometria e revelou-se uma função exclusivamente da geometria. Biemüller et al. 1996, investigou numericamente as características do escoamento turbulento em dois canais retangulares conectados por uma fenda, junto a parede superior, usando Simulação de Grandes Escalas, SGE. A altura e largura do canal eram, respectivamente, 180 e 331,6 mm e seu comprimento 504 mm. A fenda que conecta os dois canais principais possui altura, g, e largura, d, de 10,20 e 40,6 mm, respectivamente, portanto uma relação g/d=4. No domínio computacional a seção transversal foi considerada infinita, com condições de contorno periódicas nesta
Resumo. O propósito deste trabalho numérico/experimental é investigar o desenvolvimento e as cara... more Resumo. O propósito deste trabalho numérico/experimental é investigar o desenvolvimento e as características do escoamento ao longo de feixe de tubos com placas defletoras. O banco de tubos possui duas linhas, com razão de espaçamento P/D=1,26 e comprimento de 450 mm, onde existem duas placas defletoras direcionando o escoamento principal e criando uma entrada assimétrica no feixe de tubos. O número de Reynolds foi calculado utilizando-se o diâmetro externo do tubo e a velocidade de entrada, 3.32 x 10 4 . A distribuição de velocidade foi obtida experimentalmente empregando anemometria de fio quente e para a análise numérica utilizou-se o programa CFX versão 5.6. A análise numérica foi feita baseada na Simulação de Grandes Escalas (Large Eddy Simulation -LES), com o modelo de Smagorinsky e nas Equações de Navier-Stokes médias de Reynolds (Reynolds Averaged Navier-Stokes Equations-RANS), com o modelo κ-ε. O campo de pressões médias na parede lateral do banco também foi analisado. Os resultados numéricos e experimentais apresentaram boa concordância para os campos médios de velocidades e pressões. Palavras chave: banco de tubos, placas defletoras, turbulência experimental, simulação de grandes escalas, equações médias de Reynolds A utilização de placas defletoras em feixe de tubos é muito difundida em trocadores de calor, aumentando os níveis de turbulência do escoamento e o tempo de contato do fluido refrigerante e a superfície aquecida dos tubos. Os vórtices gerados pela turbulência influenciam a camada limite térmica dos tubos, onde o calor é trocado basicamente por condução, tornando a troca de calor mais eficiente. No entanto, a maioria dos estudos em bancos de tubos considera um escoamento incidindo uniformemente sobre os tubos, sem qualquer tipo de análise dos efeitos causados pela utilização de placas defletoras, transformando-se assim em idealizações pouco reais, Yeung e Weaver (1983). Já em reatores nucleares, estes utilizam, em geral, feixes de barras cilíndricas como elementos combustível., onde cada barra é constituída de material físsil propriamente revestido. O calor gerado pelo processo de fissão nuclear e é transferido ao fluido, que circula axialmente ao feixe de barras, sendo a otimização destas taxas é função tanto das propriedades físicas do fluido quanto das características do escoamento e do feixe de tubos (arranjo e relações de espaçamento). A tentativa de aumentar as taxas de transferência de calor em trocadores de calor, através do aumento da velocidade do fluido ou a redução das relações de espaçamento entre tubos, pode levar ao surgimento de cargas dinâmicas, induzindo vibrações, que são apontadas como uma das principais causas de falhas nos componentes de trocadores de calor, . Em , encontra-se um estudo experimental do efeito produzido pela presença de um defletor em um feixe de tubos. O escoamento turbulento era desviado pelo defletor atingindo o banco de tubos com um ângulo de incidência diferente de 90º. Os resultados de pressões e flutuações de pressão medidas em torno da parede de um tubo instrumentado no interior do banco de tubos, apresentaram maiores valores do que no escoamento transversal. Apareceram picos adicionais no espectro de flutuações de pressão na parede, que não puderam ser associados a nenhum dos efeitos do escoamento transversal puro nem aos efeitos produzidos somente pelo defletor. Portanto, os resultados apresentados não eram conclusivos, motivando estudos em separado, analisando o efeito causado por placas defletoras, , e um estudo experimental do escoamento através de banco de tubos inclinados, . O escoamento incidindo sobre placas defletoras, sem a utilização de tubos, foi analisado numérica e experimentalmente por . Os autores observaram o processo de separação da camada limite e a indução de recirculações do escoamento nas extremidades dos defletores, podendo significar uma importante fonte de
European Journal of Mechanics - B/Fluids, 2020
The aim of this work is to perform a numerical simulation of the turbulent flow in an eccentric c... more The aim of this work is to perform a numerical simulation of the turbulent flow in an eccentric channel for a Reynolds number Re Dh = 7300. The Reynolds number is based on the bulk velocity, U Bulk , the hydraulic-diameter, D h , and the kinematic viscosity, ν. To achieve this goal, a hybrid RANS/LES turbulence model called DES-SST is used. In this formulation, special functions are computed to convert the model from RANS close to the walls to LES in more remote regions. Besides the Reynolds number, the main dimensionless parameter related to the geometry involves the narrow gap between the outer and inner walls of the pipes and their diameters, D and d, respectively. These geometric parameters are related to the eccentricity, e, and the d/D ratio. Both of these parameters were kept constant at 0.80 and 0.50, respectively, throughout the work, as the channel's length, L = 1500 mm. The numerical results are compared with experimental outcomes for a water channel with the same Reynolds number using PIV measurements. The hybrid scheme was able to capture the onset of gap instability, short after the channel's inlet. Furthermore, the mass flow distribution along the channel and the flow velocity patterns were also successfully predicted by the numerical code. The Strouhal number was found to be in fair agreement with the experimental result. The large-scale structures were found to spread over the whole cross-section. The main frequency produced by the oscillatory motion in the tight gap was seen to be twice as high as that found in the lateral subchannel.
Uncertainty Modeling: Fundamental Concepts and Models
This chapter presents an overview of computational models and formulations, a description of some... more This chapter presents an overview of computational models and formulations, a description of some error estimators in Boundary Element Methods (BEM) and in Finite Element Methods (FEM), and some perspectives of the use of these error estimators in Bayesian approaches for Model Validation.
Otimização Geométrica De Escoamentos Com Convecção Forçada Sobre Um Arranjo De Quatro Cilindros
O presente estudo consiste na avaliacao numerica de um arranjo formado por quatro cilindros subme... more O presente estudo consiste na avaliacao numerica de um arranjo formado por quatro cilindros submetidos a um escoamento transiente, bidimensional, incompressivel, laminar e com conveccao forcada. A avaliacao geometrica e realizada atraves do metodo Design Construtal. O problema possui uma restricao dada pela soma da area dos cilindros e tres graus de liberdade: ST1/D (razao entre o passo transversal dos cilindros frontais e o diâmetro dos cilindros), ST2/D (razao entre o passo transversal dos cilindros posteriores e o diâmetro dos cilindros) e SL/D (razao entre o passo longitudinal dos cilindros frontais e posteriores e o diâmetro dos cilindros). Para todas as simulacoes sao considerados numeros de Reynolds e Prandtl constantes, ReD = 100 e Pr = 0.71. As equacoes de conservacao de massa, quantidade de movimento e energia sao resolvidas atraves do Metodo dos Volumes Finitos (FVM). O principal objetivo e avaliar o efeito dos graus de liberdade sobre o coeficiente de arrasto (C D) e o n...
Otimização Geométrica De Escoamentos Com Convecção Forçada Sobre Um Arranjo Triangular De Corpos Rombudos Quadrados
O presente estudo consiste na avaliacao numerica de um arranjo triangular de corpos rombudos subm... more O presente estudo consiste na avaliacao numerica de um arranjo triangular de corpos rombudos submetidos a um escoamento transiente, bidimensional, incompressivel, laminar e com conveccao forcada. A avaliacao geometrica e realizada atraves do metodo Design Construtal. O problema possui uma restricao dada pela soma da area dos corpos rombudos e dois graus de liberdade: ST/D (razao da distância entre o centro dos corpos rombudos posteriores e a dimensao de suas arestas), SL/D (razao da distância longitudinal entre os centros dos corpos rombudos, frontal e posteriores, e a dimensao de suas arestas). Para todas as simulacoes sao considerados numeros de Reynolds e Prandtl constantes, ReD=100 e Pr = 0.71. As equacoes de conservacao de massa, quantidade de movimento e energia sao resolvidas atraves do Metodo dos Volumes Finitos (FVM). O principal objetivo e avaliar o efeito dos graus de liberdade sobre o coeficiente de arrasto (CD) e o numero de Nusselt (NuD) entre os corpos rombudos e o es...
Constructal Design Applied to a Channel with Triangular Fins Submitted to Forced Convection
Defect and Diffusion Forum, 2017
The purpose of this work is to present a numerical study of a two-dimensional channel with two tr... more The purpose of this work is to present a numerical study of a two-dimensional channel with two triangular fins submitted to a laminar flow with forced convection heat transfer, evaluating the geometry of the first fin through the Constructal Design method. The main objectives are to maximize the heat transfer rate and minimize the pressure difference between the inlet and outlet flow of the channel for different dimensions of the first channel fin, considering the same Reynolds (ReH = 100) and Prandtl numbers (Pr = 0.71). The problem is subjected to three constraints given by the channel area, fin area and maximum occupancy area of each fin. The system has three degrees of freedom. The first is given by the ratio between height and length of the channel, which is kept fixed, H/L = 0.0625. The other two are the ratio between height and width of the upstream fin base (H3/L3) positioned on the lower surface of the channel, and the ratio between height and width of the downstream fin (H4/L4) positioned on the upper surface of the channel, which is also kept fixed, H4/L4 = 1.11. The problem is simulated for three different values of the fraction area of upstream fin (φ1 = 0.1, 0.2 and 0.3). For the numerical approach of the problem, the conservation equations of mass, momentum and energy are solved using the finite volume method (MVF). The results showed that a ratio of φ1 = 0.2 is the one that best meets the proposed multi-objective. It was also observed that φ1 = 0.1 led to a better fluid dynamics performance with a ratio between the best and the worst performance for fluid dynamics case of 25.2 times. For φ1 = 0.3, the best thermal performance is achieved, where the optimal case has a performance 65.75% higher than that reached for the worst case.
Geometric Evaluation of Forced Convective Flows across an Arrangement of Four Circular Cylinders
Defect and Diffusion Forum, 2017
The present study consists in a numerical evaluation of an arrangement formed by four cylinders s... more The present study consists in a numerical evaluation of an arrangement formed by four cylinders submitted to an unsteady, two-dimensional, incompressible, laminar and forced convective flow. The geometric evaluation is performed through the Constructal Design method. The problem has two restrictions given by the sum of the area of the cylinders and one occupation area and has three degrees of freedom: ST1/D (the ratio between the transverse pitch of the frontal cylinders and the diameter of the cylinders), ST2/D (the ratio between the transverse pitch of the posterior cylinders and the diameter of the cylinders) and SL/D (ratio between the longitudinal pitch of the frontal and posterior cylinders and the diameter of the cylinders). For all simulations the Reynolds number is kept constant, ReD = 100, and two different Prandtl numbers of Pr = 0.71 and 5.83 are considered, which simulates respectively the use of air and water as a fluid. The conservation equations of mass, momentum and energy are solved with the Finite Volume Method (FVM). The main objective is to evaluate the effect of the degrees of freedom on the drag coefficient (CD) and the Nusselt number (NuD) between the cylinders and the surrounding flow, as well as the optimal ST2/D values for three ratios of ST1/D = 1.5, 3.0 and 4.0, these results being obtained for ratios of SL/D = 1.5 and 4.0. Results showed that the ratio changes of ST1/D and ST2/D have a great influence on the drag coefficients and on the Nusselt number of the arrangement formed by the four cylinders, as well as on the geometries leading to the best fluid dynamics and thermal performance.