Simulação numérica do escoamento intermitente utilizando uma metodologia híbrida baseada no acoplamento dos modelos de captura de golfadas e de seguimento de pistões

• Ano de defesa: 2017
• Autor(a) principal: Almeida, Vinícius Rodrigues de
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Tecnológica Federal do Paraná; Curitiba; Brasil; Programa de Pós-Graduação em Engenharia Mecânica e de Materiais; UTFPR
• Palavras-chave em Português: Engenharia térmica; Métodos de simulação; Modelos matemáticos; Mecânica dos fluidos; Heat engineering; Simulation methods; Mathematical models; Fluid mechanics; CNPQ::ENGENHARIAS::ENGENHARIA MECANICA::FENOMENOS DE TRANSPORTE::MECANICA DOS FLUIDOS; Engenharia Mecânica
• Link de acesso: http://repositorio.utfpr.edu.br/jspui/handle/1/2390

The slug flow consists of the intermittent repetition of liquid slugs and elongated bubbles, and it is a common flow regime in oil production and nuclear industry. Even though many studies have been conducted, the understanding of this flow pattern is not yet completely understood in the literature. There are some difficulties in modeling the phenomenon of slug initiation and influence of the change of direction. In addition, the intermittent downward flow and the transition to the stratified regime is not well understood. In a recent work, Conte (2014) used a Lagrangian model, based on the two-fluid model for the one-dimensional and isothermal case, to simulate the slug initiation. The disadvantage is the relatively high computational time. Another methodology to simulate the evolution of slugs, also Lagrangian and one-dimensional, is the Rodrigues (2009) slug tracking model. It has a low computational cost, but requires the properties of the flow at the inlet of the pipeline to be known. The purpose of this work is to present a methodology for the coupling of the slug capturing and slug tracking models and to implement a computational routine capable of working with both models simultaneously. It will be possible to simulate the slug initiation at the entrance of the pipeline, and to follow the development of the slugs at a lower computational cost. In order to do that, the slug capturing model is used to simulate the formation of the slugs and the effects when there is change of direction in the pipe. The slug tracking model tracks the unit cells in straight sections. The hybrid methodology proposed in this work was able to predict the main flow variables at any position in the pipeline: bubble and slug lengths, slug frequency, pressure and void fraction in the bubble region. A good agreement in the results was observed, along with a computational cost of less than 50% of the hybrid methodology in relation to a pure slug capturing. It is also possible to start-up the program with experimental data at the inlet of the pipeline using the slug tracking model, and to use the slug capturing to evaluate the influence when there is a change of direction from horizontal to descending. For this second case, the results were compared with experimental data, observing that the methodology was able to predict the cases in which there is transition to the stratified flow.