Unsteady shock wave propagation through ducts has many applications, ranging from blast wave shelter design to advanced high-speed propulsion systems. The research objective of this study was improved fundamental understanding of the transient flow structures during unsteady shock wave propagation through rectangular ducts with varying cross-sectional area. This research focused on the fluid dynamics of the unsteady shock-induced flow fields, with an emphasis placed on understanding and characterizing the mechanisms behind flow compression (wave structures), flow induction (via shock waves), and enhanced mixing (via shock-induced viscous shear layers). A theoretical and numerical (CFD) parametric study was performed, in which the effects of these parameters on the unsteady flow fields were examined: incident shock strength, area ratio, and viscous mode (inviscid, laminar, and turbulent). Two geometries were considered: the backward-facing step (BFS) geometry, which provided a benchmark and conceptual framework, and the splitter plate (SP) geometry, which was a canonical representation of the engine flow path. The theoretical analysis was inviscid, quasi-1D and quasi-steady; and the computational analysis was fully 2D, time-accurate, and viscous. The theory provided the wave patterns and primary wave strengths for the BFS geometry, and the simulations verified the wave patterns and quantified the effects of geometry and viscosity. It was shown that the theoretical wave patterns on the BFS geometry can be used to systematically analyze the transient, 2D, viscous flows on the SP geometry. This work also highlighted the importance and the role of oscillating shock and expansion waves in the development of these unsteady flows. The potential for both upstream and downstream flow induction was addressed. Positive upstream flow induction was not found in this study due to the persistent formation of an upstream-moving shock wave. Enhanced mixing was addressed by examining the evolution of the unsteady shear layer, its instability, and their effects on the flow field. The instability always appeared after the reflected shock interaction, and was exacerbated in the laminar cases and damped out in the turbulent cases. This research provided new understanding of the long-term evolution of these confined flows. Lastly, the turbulent work is one of the few turbulent studies on these flows.

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Orientador: Eugênio Spanó Rosa / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-23T04:15:03Z (GMT). No. of bitstreams: 1 Souza_MarcoAntonioSampaioFerrazde_D.pdf: 6867490 bytes, checksum: 80a84e4d200eeba5b304454e706824a5 (MD5) Previous issue date: 2013 / Resumo: A fração de vazio é um parâmetro essencial para a descrição da estrutura do escoamento intermitente gás-líquido. Na produção de petróleo, por exemplo, em sistemas de elevação artificial, a técnica de gas-lift é muito utilizada em poços verticais para aumentar a produção e requer a previsão dos fenômenos que influenciam o escoamento intermitente para sua otimização. Estes efeitos incluem principalmente as distribuições radial e axial da fração de vazio. Neste trabalho medidas da fração de vazio no pistão de líquido e na bolha alongada em escoamento bifásico vertical ascendente de ar-água no padrão intermitente em golfadas foram realizadas em diversas razões de vazões de gás e líquido utilizando uma sonda elétrica e um sensor de impedância de anéis. Com um conjunto formado por dois sensores de impedância de anéis gêmeos espaçados entre si foi monitorada a passagem dos pistões de líquido e das bolhas alongadas e foram determinados os comprimentos dos pistões e das bolhas assim como a velocidade de translação do nariz da bolha alongada em uma tubulação de 26 mm de diâmetro. As técnicas de medidas foram validadas resolvendo as equações resultantes do balanço volumétrico na célula unitária com os valores das frações de vazio do pistão de líquido, da bolha alongada e da unidade e das velocidades, comprimentos e frequências obtidos experimentalmente. Esta validação tem por objetivo mostrar a consistência que as medidas experimentais apresentam com o modelo físico conferindo às medidas um alto grau de confiabilidade. Os resultados das frações de vazio do pistão de líquido, da bolha alongada e da unidade pistão-bolha foram comparados com correlações disponíveis na literatura assim como os resultados das frações de líquido do pistão de líquido foram comparados e analisados com os modelos fenomenológicos de fração de líquido disponíveis. Com os testes utilizando a sonda elétrica foi possível levantar além da distribuição axial a distribuição radial da fração de vazio local na seção transversal da tubulação. Os resultados obtidos demonstram a consistência das técnicas de medidas e permitem discutir vários fenômenos que influenciam o escoamento bifásico vertical ascendente de ar-água no padrão intermitente em golfadas / Abstract: The void fraction is an essential parameter for describing the structure of the gas-liquid slug flow. In oil production, for example, in artificial lift systems, the gas-lift technique is widely used in vertical wells to increase the production and requires the prediction of the phenomena which influence the slug flow optimization. These effects primarily include axial and radial distributions of void fraction. In this work measures the void fraction of the liquid piston and the elongated bubble in two-phase flow vertical upward air-water in slug flow pattern were performed at various ratios of gas and liquid flow rates using an electric probe and a rings impedance sensor. With a set of two twin rings impedance sensors spaced was monitored passage of liquid slugs and elongated bubbles and were determined and the lengths of the pistons and bubbles as well as the translation velocity of the nose elongated bubble in a pipe 26 mm id. The measurement techniques were validated by solving the equations resulting from the volume balance in unit cell with the values of the void fractions of the piston liquid, the bubble elongated and the unit and velocities, lengths and frequencies obtained experimentally. This validation is to show the consistency with the experimental measurements show the physical model measures conferring a high degree of reliability. The results of the void fractions of the liquid piston, the elongated bubble and bubble-piston unit were compared with correlations available in the literature and the results of the liquid fractions of liquid piston were compared and analyzed with phenomenological models of liquid fraction available. With the tests using the electric probe was possible to rise beyond of the axial distribution the radial distribution of local void fraction in the cross section of the pipe. The results demonstrate the consistency of measurement techniques and allow discuss various phenomena that influence the two-phase flow in vertical upward air-water slug flow pattern / Doutorado / Termica e Fluidos / Doutor em Engenharia Mecânica