EE - Escola de Engenharia
URI permanente desta comunidadehttps://rihomolog.furg.br/handle/1/512
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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.
- 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.
- 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.
- 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.
- 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.