EE - Trabalhos apresentados em eventos
URI permanente para esta coleçãohttps://rihomolog.furg.br/handle/1/515
Navegar
13 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.
- ItemSimulação numérica de um dispositivo de aproveitamento da energia das ondas do tipo coluna de água oscilante: comparação de dois códigos numéricos(2010) Conde, José Manuel Paixão; Teixeira, Paulo Roberto de Freitas; Didier, Eric LionelNeste artigo apresentam-se os resultados da aplicação de dois códigos numéricos na simulação de um dispositivo de aproveitamento da energia das ondas do tipo coluna de água oscilante. Um dos códigos (FLUINCO) é baseado na técnica dos elementos finitos e o outro (FLUENT) na técnica dos volumes finitos. O objectivo do trabalho consiste na validação destes códigos para este tipo de escoamento, com o intuito de os aplicar de forma sistemática no projecto de sistemas de aproveitamento de energia das ondas. O caso simulado, que corresponde a um modelo simplificado testado experimentalmente, permitiu concluir da boa qualidade dos resultados obtidos, existindo uma boa correspondência entre os resultados experimentais e os obtidos pelos códigos numéricos.
- ItemApplicability of the gaussian distribution heat source model to the thermal simulation of welding processes(2013) Araújo, Douglas Bezerra de; Teixeira, Paulo Roberto de Freitas; Cunda, Luiz Antonio Bragança daWelding processes are considered a thermal-mechanical-metallurgical coupled issue. The most important boundary condition in the 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 analyzed 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.
- ItemEstudo de metodologias para análise numérica do campo de temperatura no processo de soldagem MIG em chapas de aço inoxidável AISI 304L(2014) Farias, Rodrigo Martins; Teixeira, Paulo Roberto de Freitas; Araújo, Douglas Bezerra deOs processos de soldagem em chapas envolvem fenômenos físicos e químicos muito complexos e, por isso, difíceis de serem modelados matematicamente. Embora os efeitos termo-mecânico-metalúrgico acoplados sejam importantes, na maioria dos casos são encontrados bons resultados considerando modelos numéricos baseados nas equações da transferência de calor e nas que governam o comportamento estrutural das chapas. De modo geral, o campo térmico é independente do estrutural, permitindo que as soluções sejam realizadas em sequência (térmicoestrutural), sem necessidade de acoplamento. As análises mais adequadas dos processos de soldagem com deposição de material usam a técnica denominada de “element birth and death”, a qual considera a ativação dos elementos pertencentes ao cordão de uma malha de elementos finitos a medida que a fonte de calor se movimenta. Neste trabalho, são apresentadas análises numéricas de soldagem de topo multipasse, com chanfro em V, de chapas de aço inoxidável AISI 304L através do processo MIG convencional. As chapas possuem 9,6 mm de espessura, 200 mm de comprimento e 50 mm de largura. As simulações numéricas são realizadas no software Ansys Multiphysics®, considerando os fenômenos de convecção e radiação, e propriedades térmicas do material (condutividade térmica, calor específico e massa específica) como dependentes da temperatura. A fonte de calor móvel é do tipo Gaussiana. Os formatos da poça de fusão, obtidos dos experimentos desenvolvidos no Laboratório de Pesquisa em Engenharia da Soldagem (LAPES – FURG) são comparados com os resultados das simulações numéricas. Um dos inconvenientes na aplicação da técnica element birth and death é o fato de que os elementos pertencentes aos passes intermediários têm suas fronteiras vizinhas aos elementos dos outros passes, sendo impedidos, dessa forma, de contemplar os efeitos de radiação. Assim, comparou-se os resultados de dois códigos: o primeiro que adota o método clássico, onde ocorre o impedimento de radiação para os elementos pertencentes aos passes intermediários, e outro que considera os efeitos de radiação no processo. Observou-se diferenças nos resultados pelo uso dos dois algoritmos, concluindo-se que os efeitos de radiação são muito importantes na região de deposição de material.
- ItemNumerical analysis of regular waves over an onshore oscillating water column(2010) Davyt, Djavan Perez; Teixeira, Paulo Roberto de Freitas; Ramalhais, Rúben dos Santos; Didier, Eric LionelThe potential of wave energy along coastal areas is a particularly attractive option in regions of high latitude, such as the coasts of northern Europe, North America, New Zealand, Chile and Argentina where high densities of annual average wave energy are found (typically between 40 and 100 kW/m of wave front). Power estimated in the south of Brazil is 30kW/m, creating a possible alternative of source energy in the region. There are many types and designs of equipment to capture energy from waves under analysis, such as the oscillating water column type (OWC) which has been one of the first to be developed and installed at sea. Despite being one of the most analyzed wave energy converter devices, there are few case studies using numerical simulation. In this context, the numerical analysis of regular waves over an onshore OWC is the main objective of this paper. The numerical models FLUINCO and FLUENT® are used for achieving this goal. The FLUINCO model is based on RANS equations which are discretized using the two-step semi-implicit Taylor-Galerkin method. An arbitrary lagrangean eulerian formulation is used to enable the solution of problems involving free surface movements. The FLUENT® code (version 6.3.26) is based on the finite volume method to solve RANS equations. Volume of Fluid method (VOF) is used for modeling free surface flows. Time integration is achieved by a second order implicit scheme, momentum equations are discretized using MUSCL scheme and HRIC (High Resolution Interface Capturing) scheme is used for convective term of VOF transport equation. The case study consists of a 10.m deep channel with a 10 m wide chamber at its end. One meter high waves with different periods are simulated. Comparisons between FLUINCO and FLUENT results are presented. Free surface elevation inside the chamber; velocity distribution and streamlines; amplification factor (relation between wave height inside the chamber and incident wave height); phase angle (angular difference between the wave inside and outside the chamber); and sloshing parameter to quantify it inside the chamber are analised. Finally, a discussion of the potential and limitations of each numerical model as well as the behaviour of the onshore OWC device is presented.
- 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.