EE - Escola de Engenharia
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/512
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9 resultados
Resultados da Pesquisa
- ItemAnálise numérica da propagação de ondas na costa do Rio Grande do Sul entre Torres e Mostardas(2008) Silva, Jair Vignolle da; Teixeira, Paulo Roberto de Freitas; Calliari, Lauro JúlioO objetivo deste trabalho é o analisar numericamente a variação de energia de ondas nesta região, investigando a influência das variações da largura da plataforma interna e da largura de antepraia, e da fricção com o fundo nos processos morfodinâmicos costeiros, usa-se como ferramenta de processamento o programa REF/DIF1 (Kirby e Darlymple, 1994). Os resultados considerando um coeficiente de atrito fw.=.0,01, usado no código do REF/DIF1, foram comparados com os obtidos sem a presença do atrito, observando-se pouca influência do atrito com o fundo sobre a transformação das ondas. Adotando-se um coeficiente de atrito de fw.=.0,2, constatou-se, de forma geral, que a influência do aumento da largura da antepraia do sul de Pinhal para o norte no atrito com o fundo é compensada pela influência da diminuição da largura da plataforma continental interna.
- 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.
- 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.
- ItemComputational modeling of a regular wave tank(2009) Gomes, Mateus das Neves; Olinto, Cláudio Rodrigues; Rocha, Luiz Alberto Oliveira; Souza, Jeferson Avila; Isoldi, Liércio AndréThis paper presents two different numerical methodologies to generate regular gravity waves in a wave tank. We performed numerical simulations of wave generation through the FLUENT® package, using the Volume of Fluid (VOF) multiphase model to reproduce the wave propagation in the tank. Thus it was possible to analyze two methods for generating regular waves that could be used in future work, especially in the study of devices of energy conversion from ocean waves into electrical energy.
- ItemAnálise numérica da propagação de ondas na costa do Rio Grande do Sul entre Torres e Mostardas(2008) Silva, Jair Vignolle da; Teixeira, Paulo Roberto de FreitasAo longo do litoral norte e médio do RS, entre Torres e Mostardas, o relevo do fundo é homogêneo, suave, íngreme e com variações batimétricas e sedimentológicas da antepraia e da plataforma continental interna. Ao norte de Pinhal, a plataforma interna é mais larga, enquanto que a largura de antepraia é mais estreita. O oposto ocorre ao Sul de Pinhal. O objetivo deste trabalho é o de analisar numericamente a variação de energia de ondas nesta região, investigando a influência das variações da largura da plataforma interna e da largura de antepraia, e da fricção com o fundo nos processos morfodinâmicos costeiros. Para tal, usa-se como ferramenta de processamento o programa REF/DIF1 (Kirby e Darlymple, 1994), que é um modelo de propagação e deformação da agitação marítima em zonas de profundidade variável, baseado na aproximação parabólica da equação do declive suave. O modelo considera os efeitos de refração, difração, empolamento e dissipação de energia por atrito com o fundo e por rebentação. Baseando-se em estudos do clima de ondas da região, efetuaram-se simulações numéricas decorrentes da combinação de períodos de onda, alturas significativas e direções de propagação, com e sem atrito com o fundo. Primeiramente foi analisado o padrão de refração de ondas na região, realizando simulações de ondas de período T=9s e altura significativa de Hs=2m para diversos ângulos de incidência. Desta análise, conclui-se que o padrão dominante para essa região é o divergente. Entretanto, notaram-se convergências ao sul de Quintão, para ondas vindas dos quadrantes sudeste e sul, devido à presença do Banco da Berta, que causa um foco quase permanente. Para a análise da influência das larguras da plataforma interna e da antepraia e da fricção do fundo sobre a energia das ondas, foram propostas modelagens para onda de T=9s, Hs=2m; onda modal (T=7s, Hs=1,75m); onda de projeto (T=16s, Hs=4,8m) e onda de tempestade (T=12s, Hs=4m). Observou-se, de forma geral, um equilíbrio na atenuação da onda causada pelo atrito com o fundo ao longo da costa em estudo, indicando que a influência do aumento da largura da antepraia do sul de Pinhal para o norte no atrito com o fundo é compensada pela influência da diminuição da largura da plataforma continental interna.
- ItemEstudo para o desenvolvimento de um previsor descargas elétricas atmosféricas aplicado à região costeira do estado do Rio de Janeiro(2005) Zepka, Gisele dos Santos; Gomes, Sebastião Cícero PinheiroThe atmospheric dynamics evidently is very complex. There are many macro and micron scales processes and meteorological variables involved in the atmospheric physical phenomena. The storms with electrical dischargesare distinguished, among these phenomena, by the damage consequences to the human beings, directly or indirectly. Many researchers have pursued the possibility of forecasting the occurrence of a storm with electrical discharges, principally in the last three decades. However, there are not improvements in forecast performance, mainly due to phenomenon complexity. The main objective of the present dissertation was to accomplish a study to determine the viability or not of constructing a forecast system of atmospheric electrical discharges from artificial intelligence techniques, specifically artificial neural networks (NN). The base of the system was constituted of numerical simulations results of the atmospheric dynamics obtained from the mesoscale model MM5. It was identified meteorological variables (outputs of MM5) that would have some correlation with the electrical discharges. These variables act as input in the NN, which generate the forecast, consisting in the number of electrical discharges that will reach the ground some posterior time to the relative time of the simulated atmospheric fields. The region chosen for this study includes the state of Rio de Janeiro, the south of Espírito Santo, the southeast of Minas Gerais and the AtlanticOcean. Besides possessing a detection system of electrical discharges, this region contains the most important concentration of oil platforms of Brazil, being strategic to better know the atmospheric behavior in this place. Before developing the forecast system based on NN, some comparative tests were made using the MM5 simulation results and GOES infrared imagery, in order to survey the model prognostic capability. The forecast system showed reasonable results, indicating that the NN application may be a promising way to the electrical discharge forecast. However, it is necessary a better investigation, mainly with relation to the accomplishment of others tests with a bigger set of electrical discharges real data.
- ItemThermal Model for Electromagnetic Launchers(2008) Zhao, Hairong; Souza, Jeferson Avila; Ordonez, Juan CarlosThis paper presents a 3D model for the determination of the temperature field in an electromagnetic launcher. The large amounts of energy that are dissipated into the structure of an electromagnetic launcher during short periods of time lead to a complicated thermal management situation. Effective thermal management strategies are necessary in order to maintain temperatures under acceptable limits. This paper constitutes an attempt to determine the temperature response of the launcher. A complete three-dimensional model has been developed. It combines rigid body movement, electromagnetic effects and heat diffusion together. The launcher consists of two parallel rectangular rails and an armature moving between them. Preliminary results show the current distribution on the rail cross-section, the localized resistive heating, and the rail transient temperature response. The simulation results are compared to prior work presented for a 2D geometry by Powell and Zielinski (2008).
- ItemHexahedral modular bioreactor for solid state bioprocesses(2009) Cunha, Daniele Colembergue da; Souza, Jeferson Avila; Rocha, Luiz Alberto Oliveira; Costa, Jorge Alberto VieiraThe design of a modular bioreactor for solid state fermentation is a promising development because it keeps the homogeneity of the bed at optimal levels. This study determines the optimum geometry of elementary modules of hexahedral bioreactors subjected to constant volume. The bioreactors have a square section and do not need an external cooling system, because the optimization limits the temperature of the bed to 35 C. The geometric optimization followed the Constructal principle of minimum heat resistance. The numerical simulations take into account the following parameters: inlet air temperature and velocity, and module volume. Once the elementary module has been selected, the total volume of the bioreactor can be calculated.
- ItemTwo-dimensional Control Volume Modeling of the Resin Transfer in a Porous Media with a Heterogeneous Permeability Tensor(2008) Souza, Jeferson Avila; Nava, Marcelo José Anghinoni; Rocha, Luiz Alberto Oliveira; Amico, Sandro CamposResin Transfer Molding (RTM) is a polymer composite processing technique widely used in the aeronautics and automotive sectors. This paper describes the numerical simulation of the RTM process where Darcy’s law was used for the mathematical formulation of the problem. A control volume finite element method was used for the determination of pressure gradients inside the mold, and a geometric reconstruction algorithm is used for the resin flow-front determination. Permeability of the medium was considered either a constant or a two dimensional tensor. The application was validated by direct comparison with literature data and good qualitative and quantitative agreement was obtained. The finite volume method was built to be used with a two-dimensional unstructured grid, hence allowing the analysis of complex geometries. The results showed that the proposed methodology is fully capable of predicting resin flow advancement in a multi-layer (with distinct physical properties) reinforced media.