6 resultados para Maximum nodal injection
Resumo:
Reliable flow simulation software is inevitable to determine an optimal injection strategy in Liquid Composite Molding processes. Several methodologies can be implemented into standard software in order to reduce CPU time. Post-processing techniques might be one of them. Post-processing a finite element solution is a well-known procedure, which consists in a recalculation of the originally obtained quantities such that the rate of convergence increases without the need for expensive remeshing techniques. Post-processing is especially effective in problems where better accuracy is required for derivatives of nodal variables in regions where Dirichlet essential boundary condition is imposed strongly. In previous works influence of smoothness of non-homogeneous Dirichlet condition, imposed on smooth front was examined. However, usually quite a non-smooth boundary is obtained at each time step of the infiltration process due to discretization. Then direct application of post-processing techniques does not improve final results as expected. The new contribution of this paper lies in improvement of the standard methodology. Improved results clearly show that the recalculated flow front is closer to the exact one, is smoother that the previous one and it improves local disturbances of the exact solution.
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Undesirable void formation during the injection phase of the liquid composite molding process can be understood as a consequence of the non-uniformity of the flow front progression, caused by the dual porosity of the fiber perform. Therefore the best examination of the void formation physics can be provided by a mesolevel analysis, where the characteristic dimension is given by the fiber tow diameter. In mesolevel analysis, liquid impregnation along two different scales; inside fiber tows and within the spaces between them; must be considered and the coupling between these flow regimes must be addressed. In such case, it is extremely important to account correctly for the surface tension effects, which can be modeled as capillary pressure applied at the flow front. When continues Galerkin method is used, exploiting elements with velocity components and pressure as nodal variables, strong numerical implementation of such boundary conditions leads to ill-posing of the problem, in terms of the weak classical as well as stabilized formulation. As a consequence, there is an error in mass conservation accumulated especially along the free flow front. This article presents a numerical procedure, which was formulated and implemented in the existing Free Boundary Program in order to significantly reduce this error.
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Journal of Hydraulic Engineering, Vol. 135, No. 11, November 1, 2009
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Dissertao para obteno do Grau de Mestre em Engenharia Electrotcnica e de Computadores
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One of the biggest challenges for humanity is global warming and consequently, climate changes. Even though there has been increasing public awareness and investments from numerous countries concerning renewable energies, fossil fuels are and will continue to be in the near future, the main source of energy. Carbon capture and storage (CCS) is believed to be a serious measure to mitigate CO2 concentration. CCS briefly consists of capturing CO2 from the atmosphere or stationary emission sources and transporting and storing it via mineral carbonation, in oceans or geological media. The latter is referred to as carbon capture and geological storage (CCGS) and is considered to be the most promising of all solutions. Generally it consists of a storage (e.g. depleted oil reservoirs and deep saline aquifers) and sealing (commonly termed caprock in the oil industry) formations. The present study concerns the injection of CO2 into deep aquifers and regardless injection conditions, temperature gradients between carbon dioxide and the storage formation are likely to occur. Should the CO2 temperature be lower than the storage formation, a contractive behaviour of the reservoir and caprock is expected. The latter can result in the opening of new paths or re-opening of fractures, favouring leakage and compromising the CCGS project. During CO2 injection, coupled thermo-hydro-mechanical phenomena occur, which due to their complexity, hamper the assessment of each relative influence. For this purpose, several analyses were carried out in order to evaluate their influences but focusing on the thermal contractive behaviour. It was finally concluded that depending on mechanical and thermal properties of the pair aquifer-seal, the sealing caprock can undergo significant decreases in effective stress.
Resumo:
O objetivo desta dissertao a determinao da mxima injeo nodal numa rede de energia eltrica, ou seja, qual o valor total mximo de potncia ativa que possvel injetar e qual a sua distribuio pelos diversos ns da rede simultaneamente. Determinmos esta mxima injeo nodal em duas situaes distintas: injeo no simultnea, injetando potncia em um s n de cada vez e injeo simultnea, injetando potncia em todos os ns da rede simultaneamente. Sendo este um problema de natureza combinatria, utilizmos para esta determinao o algoritmo conhecido como nuvem ou enxame de partculas, adaptando-o ao nosso problema. Desenvolvemos o software na linguagem de programao Python utilizando o ambiente Eclipse. Para resolver o trnsito de energia utilizmos o programa PSSE University.Para os exemplos de aplicao utilizmos duas redes de energia eltrica, uma de 6 e outra de 14 barramentos. Estas redes foram baseadas nas redes IEEE 6 BUS e IEEE 14 BUS respetivamente. Conclumos que o algoritmo nuvem ou enxame de partculas cumpriu o objetivo traado, obtendo as melhores solues para cada um dos casos, mxima injeo nodal no simultnea e mxima injeo nodal simultnea. No contexto deste problema, o parmetro chave do algoritmo, comprovado pelos ensaios feitos, a velocidade mxima de deslocao das partculas, tomando valores tpicos de 7 a 10 para a rede de 6 barramentos e de 20 a 25 para a de 14 barramentos.
