Two-dimensional reactive flow simulation through a vorticity-stream function formulation with buoyant term using finite elements method

• Ano de defesa: 2017
• Autor(a) principal: Oliveira Filho, Alcéstes Guanabarino de
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade do Estado do Rio de Janeiro; Centro de Tecnologia e Ciências::Faculdade de Engenharia; BR; UERJ; Programa de Pós-Graduação em Engenharia Mecânica
• Palavras-chave em Português: Mechanical Engineering; Transport theory; Fluid mechanics; Reactive flows; Simulation; Vorticity-stream function formulation; Finite Elements Method; Engenharia Mecânica; Teoria do transporte, Mecânica dos fluidos; Escoamentos reativos; Simulação; Formulação de função-corrente e vorticidade; Método de Elementos Finitos; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA
• Link de acesso: http://www.bdtd.uerj.br/handle/1/11667

Construction of hydroelectric power plants to supply the demand for electrical energy has always been introduced coupled to the concept of harnessing of natural resources and as being more "clean" than thermoelectric production. Actually, it causes large environmental impacts because decomposition of organic matter submerged in huge reservoirs implies in generation of large volumes of greenhouse gases. Thus, it is of interest to study ways to model this phenomenon. Although reservoir flows comprise mixed water and gases, related literature states that these flows have stratified characteristics with density and temperature profiles determined by external environmental cycles. In these basins, the flow has two main components that draw attention: the longitudinal velocity, driven mainly by feeding inflow and outflow discharge and the vertical velocity, driven mainly by gas evolution to the surface. Therefore, it was decided to study a two-dimensional flow model through stream function vorticity formulation, taking into account the density profile provided by the gas given off through Boussinesq approximation. Also, in view of methane oxidation reaction within the reservoir, a decay term is added to the species transport equation, implying in a reactive flow. For the simulations, with the ultimate goal of obtaining flow velocity and concentration profiles, Finite Elements Method emerges as a viable method which can handle-diffusive convective equations, whose boundary conditions are consistently integrated in the system weak form. In view of the seasonal cycles present in environmental phenomena, multidimensional analytical solutions for transient boundary conditions are proposed. Considerations on novel boundary conditions for the transport of vorticity, more adjusted to the physical phenomena than those currently found in the bibliography are made, which is also an innovation. Results are obtained and criticized and difficulties in the implementation of the model are discussed. Suggestions for further work are also outlined.