EE - Artigos Publicados em Periódicos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/513
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11 resultados
Resultados da Pesquisa
- Item3D numerical analysis about the shape influence of the hydro-pneumatic chamber in an oscillating water column (owc).(2015) Isoldi, Liércio André; Grimmler, Juliana do Amaral Martins; Letzow, Max; Souza, Jeferson Avila; Gomes, Mateus das Neves; Rocha, Luis Alberto Oliveira; Santos, Elizaldo Domingues dosThe oceans represent one of the major energy natural resources, which potentially can be used to supply the World energy demand. In the last decades some devices to convert the wave ocean energy into electrical energy have been studied. In this work the operating principle of an Oscillating Water Column (OWC) converter was analyzed with a transient 3D numerical methodology, using the Finite Volume Method (FVM) and the Volume of Fluid (VOF) model. The incident waves on the OWC hydropneumatic chamber cause an oscillation of the water column inside the chamber producing an alternate air flow through the chimney. The air drives a turbine that is coupled to an electric generator. The aim of this work was to investigate the shape influence of the hydro-pneumatic chamber geometry in the air flow. For this, six cases were studied in laboratory scale and the results showed that the variation of the OWC chamber shape can improve 12.4% the amount of mass air flow.
- ItemSimulação numérica da ação de ondas sobre um dispositivo de captação de energias das ondas do tipo coluna de água oscilante(2011) Davyt, Djavan Perez; Teixeira, Paulo Roberto de Freitas; Ramalhais, Rúben dos Santos; Didier, Eric LionelNeste trabalho é analisado um dispositivo de extração de energia das ondas do tipo coluna de água oscilante sob a ação de ondas regulares de diferentes períodos. São realizadas variações no comprimento submerso da parede frontal e no comprimento da câmara. Para tal é utilizado o código numérico FLUINCO, o qual é baseado nas equações RANS e a discretização é realizada utilizando o método semi-implícito de Taylor-Galerkin de dois passos. Uma formulação lagrangeana-euleriana arbitrária (ALE) é utilizada para permitir a solução de problemas que envolvem movimentos da superfície livre. Alguns resultados são comparados com os obtidos utilizando o programa FLUENT. São apresentados a amplificação (relação entre a altura da onda incidente a e dentro da câmara), distribuição das velocidades e vetores de velocidade.
- ItemNumerical simulation of an oscillating water column device using a code based on Navier-Stokes equations(2013) Teixeira, Paulo Roberto de Freitas; Davyt, Djavan Perez; Didier, Eric Lionel; Ramalhais, Rúben dos SantosThe study of ways of converting ocean wave energy into a useful one and the improvement of the existing equipment are complex engineering problems and very important issues in today’s society. In this paper, the onshore oscillating water column device, in a 10 m deep channel subjected to 1 m high incident wave and wave periods from 4 s to 15 s, is investigated. The numerical analyses are carried out using Fluinco model that deals with incompressible flow problems based on the Navier-Stokes equations and employs the two-step semi-implicit Taylor-Galerkin method. An aerodynamic model is implemented in the algorithm to determine the air pressure that is imposed on the free surface. Analyses are divided into two sections. In the first section, the flow variables obtained by Fluinco and the commercial model Fluent are compared and similar results are obtained. In the second section, an investigation of the chamber geometry and turbine characteristic relation that provide the best device performance is carried out. In this case, variations in the front wall depth, the chamber length, the turbine characteristic relation and the chamber height, are made.
- ItemStudy of the gaussian distribution heat source model applied to numerical thermal simulations of TIG welding processes(2014) Teixeira, Paulo Roberto de Freitas; Araújo, Douglas Bezerra de; Cunda, Luiz Antonio Bragança daWelding processes are considered a thermal-mechanical-metallurgical coupled issue. The most important boundary condition in the numerical thermal analysis is the heat source model. Although many studies have been carried out to propose different types of heat source models, the limitations of each model application have not been clearly specified. The Gaussian heat source is a model in which heat is generated over a surface; therefore, it may not be suitable to be applied to thick plates. In this study, the accuracy of the Gaussian heat source model is investigated in bead-on-plate welding by the TIG process. Analyses are performed by the ANSYS® software, considering the convection and the radiation phenomena. Several cases with different parameters of heat distribution, heat input and plate thickness have had their weld pool geometries analysed and compared with those obtained experimentally. Analyses of the influence of the radial distance from the center of the Gaussian heat source and the thickness of the plate on the bead width and the penetrated depth of the fusion zone boundary are presented. Results have shown the adequacy and the limitations of the Gaussian heat source model in the welding simulation.
- ItemNumerical analyses of wave propagation over the inner shelf and shoreface of the southern brazilian coast: from Torres to Mostardas(2014) Silva, Jair Vignolle da; Teixeira, Paulo Roberto de Freitas; Calliari, Lauro JúlioThe shoreface and the inner shelf along the northern and the central coast of Rio Grande do Sul (RS) state, Brazil, between Torres and Mostardas, although displaying a homogeneous bottom relief show variations in slope and width. In the northern sector, between Torres and Pinhal, the inner shelf is wide, while the shoreface is narrow. Towards the south, these patterns are just the opposite. In this study, a model based on the parabolic approximation of the mild slope equation, REF/DIF.1, is used to simulate the wave propagation in this region. Wave refraction diagrams based on the predominant wave climate show a dominant and invariable divergent pattern for wave incidence from 90° to 135°. Numerical analyses of changes in wave energy, regarding differences in width and slope using a bottom friction coefficient fw = 0.01 in the different coastal sectors, show little influence of the bottom friction over the wave transformation processes. In general, a friction coefficient fw = 0.2 shows that wave energy reduction due to bottom friction over the wider shoreface south of Pinhal by comparison with the sector to the north is compensated by its shorter inner shelf width. The analyses show that lateral gradients of wave energy along the 10 m isobaths regarding the morphological differences between the two sectors are negligible.
- ItemComputational modeling of RTM and LRTM processes applied to complex geometries(2012) Porto, Joseane da Silva; Letzow, Max; Santos, Elizaldo Domingues dos; Amico, Sandro Campos; Souza, Jeferson Avila; Isoldi, Liércio AndréLight Resin Transfer Molding (LRTM) is a variation of the conventional manufacturing process known as Resin Transfer Molding (RTM). In general terms, these manufacturing processes consist of a closed mould with a preplaced fibrous preform through which a polymeric resin is injected, filling the mold completely, producing parts with complex geometries (in general) and good finish. Those processes differ, among other aspects, in the way that injection occurs. In the RTM process the resin is injected through discrete points whereas in LRTM it is injected into an empty channel (with no porous medium) which surrounds the entire mold perimeter. There are several numerical studies involving the RTM process but LRTM has not been explored enough by the scientific community. Based on that, this work proposes a numerical model developed in the FLUENT package to study the resin flow behavior in the LRTM process. Darcy’s law and Volume of Fluid method (VOF) are used to treat the interaction between air and resin during the flow in the porous medium, i.e. the mold filling problem. Moreover, two three-dimensional geometries were numerically simulated considering the RTM and LRTM processes. It was possible to note the huge differences about resin flow behavior and filling time between these processes to manufacture the same parts.
- ItemExperimental and numerical analysis of an earth-air heat exchanger(2011) Vaz, Joaquim; Sattler, Miguel Aloysio; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréThe need to develop new technologies that allow the use of sustainable alternative sources of energy is increasingly evident. Thus, this work presents an experimental and numerical study of earth–air heat exchangers, which are used to reduce consumption of conventional energy for heating and cooling of built environments through the use of thermal energy contained in the soil. The experiment was conducted in southern Brazil in the city of Viamão, and its results were used to validate the computational modeling of heat exchangers. In the present work, the variation of air temperature inside the ducts, to an annual cycle, was investigated. The numerical solution of the conservation equations of the problem is performed with a commercial code (FLUENT) which is based on the Finite Volume Method (FVM). Turbulence is tackled with the Reynolds Stress Model (RSM). The transient temperature fields predicted numerically was compared with the experimental ones, the highest difference found was lower than 15%. The results showed the validity and effectiveness of the employed computational model, enabling its use for future researches and projects developments about earth–air heat exchangers.
- ItemNumerical investigation about the improvement of the thermal potential of an Earth-Air Heat exchanger (EAHE) employing the Constructal Design method(2015) Rodrigues, Michel Kepes; Brum, Ruth da Silva; Vaz, Joaquim; Rocha, Luiz Alberto Oliveira; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréThe Earth-Air Heat Exchanger (EAHE) is a device used to improve the thermal condition of built environments, allowing the reduction of electrical energy consumption of traditional air conditioner systems. Fundamentally, its operational principle is based on fluid mechanics and heat transfer, areas in which Constructal Design has been widely used to seek for the optimal geometries, i.e., which leads to the best performances. In spite of this fact, the employment of Constructal Design for improvement of the EAHE thermal potential has not been performed into literature. Therefore, the main purpose of this work is to perform a numerical investigation on different geometrical configurations of an EAHE using the Constructal Design to obtain the highest thermal potential. Results indicated that, for the same area occupied by the ducts and fixed mass flow rate of air, the increase of the number of ducts (complexity of geometry) improved the EAHE thermal performance up to approximately 73% for cooling and 115% for heating.
- ItemElastic and elasto-plastic buckling analysis of perforated steel plates(2013) Real, Mauro de Vasconcellos; Isoldi, Liércio André; Damas, Alexandra Pinto; Helbig, DanielMany steel structures such as ships and offshore structures are composed by welded stiffened or unstiffened plate elements. Cutouts are often provided in these plate elements for inspection, maintenance, and service purposes, and the size of these holes could be significant. In many situations, these plates are subjected to axial compressive forces which make them prone to instability or buckling. If the plate is slender, the buckling is elastic. However, if the plate is sturdy, it buckles in the plastic range causing the so-called inelastic (or elasto-plastic) buckling. Furthermore, the presence of these holes redistributes the membrane stresses in the plate and may cause significant reduction in its strength in addition to changing its buckling characteristics. So, the objective of this paper is to investigate the changes that the presence of circular holes produces in the elastic and inelastic buckling of steel rectangular plates. The finite element method (FEM) has been used to evaluate the elastic and elastoplastic buckling load of uniaxially loaded rectangular plates with circular cutouts. By varying the hole diameter, the plate aspect ratio and the plate thickness during the analyses, the changes in the plate buckling behavior can be determined. The results show that while the circular hole can in some cases even increase the elastic buckling load, the elasto-plastic buckling load is reduced by the presence of the cutout.
- ItemNumerical study on the effect of submerged depth on the horizontal plate wave energy converter(2014) Seibt, Flávio Medeiros; Couto, Eduardo Costa; Santos, Elizaldo Domingues dos; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira; Teixeira, Paulo Roberto de FreitasThe growing search for clean and renewable energy sources has given rise to the studies of exploring sea wave energy. This paper is concerned with the numerical evaluation of the main operational principle of a submerged plate employed for the conversion of wave energy into electrical one. The numerical model used to solve the conservation equations of mass, momentum and transport of volume fraction is based on the finite volume method (FVM). In order to tackle with the flow of mixture of air-water and its interaction with the device, the multiphase model volume of fluid (VOF) is employed. The purpose of this study is the evaluation of a numerical model for improvement of the knowledge about the submerged plate wave energy converter, as well as the investigation of the effect of the distance from the plate to the bottom of the sea (H P) on the performance of the converter. The simulations for several distances of the plate from the seabed show that the optimal efficiency is 64%, which is obtained for H P=0.53 m (88% of the depth). This efficiency is 17% larger than that found in the worst case (H P=0.46 m, 77% of the depth).