EE - Trabalhos apresentados em eventos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/515
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8 resultados
Resultados da Pesquisa
- ItemNumerical simulation and constructal theory applied for geometric optimization of thin perforated plates subject to elastic buckling(2013) Correia, Anderson Luis Garcia; Helbig, Daniel; Real, Mauro de Vasconcellos; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréMany elements in engineering are formed by thin plates. Hulls and decks of ships are examples of application. These elements can have holes that serve as inspection port, access or even to weight reduction. The presence of holes causes a redistribution of the membrane stresses in the plate, significantly altering their stability. In this paper the Bejan’s Constructal Theory was employed to discover the best geometry of thin perforated plates submitted to elastic buckling phenomenon. To study this behavior simply supported rectangular plates with a centered elliptical perforation were analyzed. The purpose was to obtain the optimal geometry which maximizes the critical buckling load. For this, the degrees of freedom H/L (ratio between width and length of the plate) and H0/L0 (ratio between the characteristic dimensions of the hole) were varied. Moreover, different values of hole volume fraction ϕ (ratio between the perforation volume and the massive plate volume) were also investigated. A computational modeling, based on the Finite Element Method (FEM), was used for assessing the plate buckling load. The results showed that Constructal Design can be employed not only in the heat transfer and fluid flow problems, but also to define the best shapes in solid mechanics problems.
- ItemConstructal design of perforated steel plates subject to linear elastic and nonlinear elastoplastic buckling(2013) Helbig, Daniel; Real, Mauro de Vasconcellos; Correia, Anderson Luis Garcia; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréSteel plates are used in a great variety of engineering applications, such as deck and bottom of ship structures, and platforms of offshore structures. Cutouts are often provided in plate elements for inspection, maintenance, and service purposes. So, the design of shape and size of these holes is significant. Usually 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.Therefore, the goal of this work is to obtain the optimal geometry which maximizes the buckling load for steel plates with a centered elliptical perforation when subjected to linear and nonlinear buckling phenomenon by means of Constructal Design. To do so, numerical models were developed in ANSYS software to evaluate the elastic and elasto-plastic buckling loads of simply supported and uniaxially loaded rectangular plates with elliptical cutouts. The results indicated that the optimal shapes were obtained in accordance with the Constructal Principle of "Optimal Distribution of Imperfections", showing that the Constructal Design method can be satisfactorily employed in mechanic of materials problems.
- ItemAn original procedure to determine transverse permeability using a multilayer reinforcement in RTM(2010) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto Oliveira; Amico, Sandro Campos; Silva, Rafael Diego Sonaglio daResin Transfer Molding (RTM) is a manufacturing process for polymer composites parts for a variety of uses. The numerical simulation of the resin flow into the mold can be used to minimize costs related to mold design and the manufacturing process itself. However, to obtain realistic results, accurate information about the resin and the reinforcement media are necessary. In the multilayer RTM, distinct porous media layers are stacked to obtain a final composite with better performance. For the numerical simulation of the multilayer RTM, transverse permeability (Kzz) data are necessary. This work proposes an original methodology to determine the transverse permeability in multilayer RTM composites, assuming that the in-plane permeabilities (Kxx and Kyy) are known and using this information, combined with experimental data obtained during mold filling. The motivation of this study is the fact that the transverse permeability is usually not available in the literature, being referred to as a difficult parameter to be directly determined using experiments.
- ItemComputational modeling of the resin transfer molding process(2009) Oliveira, Cristiano Peres; Souza, Jeferson Avila; Isoldi, Liércio André; Rocha, Luiz Alberto de Oliveira; Amico, Sandro CamposThe Resin Transfer Molding, or RTM, process has recently become one of the most important processes of fiber reinforced composites manufacturing. The process consists essentially of three stages: “an arrangement of fiber mats in a mold cavity, a mold filling by a polymeric resin and a curing phase”. Most of the difficulties of incorporating RTM occur during the filling stage. To create an acceptable composite part the preform must be completely impregnated with resin. The conditions which most strongly influence the flow are mold geometry, resin rheology, preform permeability, and location of the injection ports and vents. There are different types of RTM process, e.g. RTM Light or VARTM, employed in accordance with the final desired characteristics and properties of composite components. Besides, RTM may also be carried out using multilayers, with distinct characteristics. The numerical simulation of the mold filling stage becomes an important tool which helps the mold designer to understand the process parameters. Considering the fibrous preform as a porous media, the phenomenon can be modeled by Darcy’s law to describe resin flow. This study used two commercial softwares, FLUENT® and PAM-RTM®. FLUENT® is a general Computational Fluid Dynamics (CFD) code, based on Finite Volume Method (FVM). It applies the Volume of Fluid (VOF) method to solve the filling problem because it does not have a specific RTM module. PAM-RTM® is a specific package for RTM problems, based on the Finite Element Method (FEM). These tools were applied to simulate numerically several RTM examples of the resin flow into the mold and the results for both softwares were compared with previous works.
- ItemConstructal design applied to the light resin transfer molding (LRTM) manufacturing process(2013) Isoldi, Liércio André; Souza, Jeferson Avila; Santos, Elizaldo Domingues dos; Marchesini, Renato; Porto, Joseane da Silva; Letzow, Max; Rocha, Luiz Alberto de Oliveira; Amico, Sandro CamposThe Light Resin Transfer Molding (LRTM) is a manufacturing process where a closed mold pre-loaded with a porous fibrous preform is filled by a liquid resin injected through an empty channel (without porous medium) which runs all around the perimeter of the mold, producing polymeric composite parts. Using the capability of FLUENT® package to simulate a multiphase flow (resin and air) in a geometry composed by porous media regions and empty regions, a computational model based on the Finite Volume Method (FVM) was applied to reproduce the resin flow behavior during the LRTM process. The aim of this work was to define the optimal geometry for the empty channel (border) by means the Constructal Design method. To do so, considering a border with a rectangular cross sectional area, the degree of freedom wb/tb (ratio between the width and thickness of the border) can vary while the border volume is kept constant. The results showed that employing the Constructal Design it is possible to decrease the filling time of the LRTM process in almost 20 %, being this an unpublished use for the Constructal Theory.
- ItemNumerical simulation of an owc devise(2013) Souza, Jeferson Avila; Santos, Elizaldo Domingues dos; Isoldi, Liércio AndréWave energy is a renewable and clean energy resource that, in a near future, may become an alternative to the more pollutant fuels. There are a number of wave energy converters prototypes and a few installed text facilities, however there is no device ready for commercial utilization. In this work an Oscillation Water Column Generator (OWC) is numerical simulated using the OpenFOAM software. The VOF (volume of fluid) method is used to solve the multiphase (air + water) fluid flow problem. Regular gravity waves, inside a rectangular (2D) tank, are imposed numerically by prescribing the inlet velocity at the left wall of the tank. The main goal of the work is to simulate the interaction between the generated waves and the OWC device and calculate the energy generated by the turbine (usually a Wells turbine). The air turbine, responsible for the electrical energy generation, is simulated by applying a source (force) term to the momentum equation at the OWC chimney section. Pressure drop at the turbine and air velocity at the chimney outlet section are evaluated as a function of time and used to compute the available energy to be converted into electrical energy. Results are presented and compared for two operating condition: with turbine and without turbine.
- ItemComputational modeling of the air-flow in an oscillating water column system(2009) Gomes, Mateus das Neves; Olinto, Cláudio Rodrigues; Isoldi, Liércio André; Souza, Jeferson Avila; Rocha, Luiz Alberto de OliveiraSeveral alternatives for electric power production have been studied in the last decades. Because of the huge energetic resources stored in the oceans in the form of wave - about 2TW - value that is compared to the annual rate of electric power used in the earth, the conversion of the wave’s energy of the oceans in electric power comes up important as one of these alternatives. One of the ways to make that conversion is through the oscillating water column (OWC) system: the wave enters into the hydro-pneumatic chamber (resembling a cave with entry below the waterline) and the up-and-down movement of water column inside the chamber makes air flow to and from the atmosphere, driving an air turbine. The turbine is symmetric and is driven indifferently in which direction the air flows. This paper presents the computational modeling of the air flow in a oscillating water column chamber using two different methodologies: in one of them it is considered just the chamber, varying the velocity in its entrance according to the wave’s equation, considering just the air, and a new one considering the chamber put into a wave’s tank, so it takes in account the complete interaction between water and air into the chamber. In this method, to consider the water and air it is used the multiphase model volume of fluid (VOF). It was simulated the same geometric compound of an oscillating water column system with a vertically placed tower, in order to compare these two different numerical models. It is noted that the dimensions of the tested chamber are in laboratory scale and the proposed model was used to simulate a 2D case. It was used GAMBIT® software for geometry creation and mesh generation, while FLUENT® package was employed for solving the conservation equations and analysis of the results.
- ItemAnálise de malhas para geração numérica de ondas em tanques(2012) Gomes, Mateus das Neves; Isoldi, Liércio André; Santos, Elizaldo Domingues dos; Rocha, Luiz Alberto OliveiraEste trabalho apresenta uma metodologia para a geração numérica de ondas em tanques e também um estudo de malhas a serem utilizadas em simulações numéricas da propagação de ondas regulares bidimensionais em tanques. São testados dois tipos de geração e refinamento de malhas. Assim busca-se encontrar uma malha independente que forneça resultados com acurácia e com menor esforço computacional. Foram realizadas simulações numéricas da geração de ondas através do pacote FLUENT® , que é baseado no Método de Volumes Finitos (MVF). Foi empregado o modelo multifásico Volume of Fluid (VOF) para reproduzir a propagação da onda no tanque. Esses resultados poderão ser utilizados em trabalhos futuros, principalmente no estudo numérico de dispositivos para conversão de energia das ondas do mar em energia elétrica, como por exemplo, os dispositivos de coluna de água oscilante (OWC) e de galgamento.