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Estudo numérico do efeito da razão do confinamento no padrão de escoamentos com rotação
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Nesta dissertação pretende-se estudar a influência da razão de confinamento no padrão de escoamentos com rotação, em condições não reativas, com recurso à ferramenta ANSYS Fluent. O domínio da simulação numérica consiste numa câmara cilíndrica, onde a rotação imposta por um gerador de rotação é simulada com a introdução de velocidade tangencial no escoamento.
O principal objetivo foi completar os estudos numéricos iniciados por Gomes (2019), contemplando agora uma gama alargada de razões de confinamento, para números inteiros 1<𝐷/𝑑≤18, de modo a nela identificar a subgama para a qual se verifica a reversão do escoamento, vórtice ingressante, à saída da câmara no centro da secção. Para além disso, foi estudado o caso de escoamento sem confinamento, 𝐷/𝑑=∞.
O modelo da câmara cilíndrica foi definido com uma geometria simplificada 2D, seme-lhante ao presente nas dissertações de Gomes (2019) e Camilo (2017), sendo o modelo de tur-bulência RSM (Reynolds Stress Model), baseado nas equações RANS. Os resultados da simula-ção foram comparados com os resultados obtidos por Gomes (2019).
Verificou-se a existência da zona de recirculação central estudada por Gomes (2019), para 𝐷/𝑑=5,4, sendo que o seu ponto de fecho ocorre para 𝑥=0,489 m, valor bastante dife-rente do que foi apresentado pela autora em 2019, 𝑥=0,190 m, devido às diferentes velocida-des tangenciais utilizadas.
Relativamente ao padrão de escoamentos não foi observada uma tendência com a vari-ação da razão de confinamento, devido à instabilidade da simulação imposta pelo regime es-tacionário. Pela mesma razão não se conseguiu captar o vórtice ingressante para as diferentes razões de confinamento, presente nos estudos experimentais de Camilo (2017) e Gomes (2019).
In this thesis it is intended to study the influence of the confinement ratio on the non-reactive swirling flows pattern, using the ANSYS Fluent tool. The numerical simulation do-main consists of a cylindrical chamber, where the rotation imposed by a swirler is simulated with the introduction of swirl velocity in the flow. The main objective was to complete the numerical studies initiated by Gomes (2019), now contemplating a wide range of confinement ratios, for integers 1<𝐷/𝑑≤18, in order to identify a subrange for which the backflow occurs, incoming vortex, at the exit of the chamber in the center of the section. Furthermore, the case of flow without confinement, 𝐷/𝑑=∞, was also studied. The cylindrical chamber model was defined with a simplified 2D geometry, similar to the model in the thesis of Camilo (2017) and Gomes (2019), with RSM (Reynolds Stress Model) being the turbulence model, based on the RANS equations. The simulation results were com-pared with the results obtained by Gomes (2019). The existence of the central recirculation zone studied by Gomes (2019) was verified, for 𝐷/𝑑=5,4, and its closing point occurs at 𝑥=0,489 m, a quite different value from that obtai-ned by the author in 2019, 𝑥=0,190 m, due to the different swirl velocities used. Regarding the flow pattern, no trend was observed with the variation of the confine-ment ratio, due to the instability of the simulation imposed by the steady state. For the same reason, it was not possible to capture the incoming vortex for the different confinement ratios, present in the experimental studies by Camilo (2017) and Gomes (2019).
In this thesis it is intended to study the influence of the confinement ratio on the non-reactive swirling flows pattern, using the ANSYS Fluent tool. The numerical simulation do-main consists of a cylindrical chamber, where the rotation imposed by a swirler is simulated with the introduction of swirl velocity in the flow. The main objective was to complete the numerical studies initiated by Gomes (2019), now contemplating a wide range of confinement ratios, for integers 1<𝐷/𝑑≤18, in order to identify a subrange for which the backflow occurs, incoming vortex, at the exit of the chamber in the center of the section. Furthermore, the case of flow without confinement, 𝐷/𝑑=∞, was also studied. The cylindrical chamber model was defined with a simplified 2D geometry, similar to the model in the thesis of Camilo (2017) and Gomes (2019), with RSM (Reynolds Stress Model) being the turbulence model, based on the RANS equations. The simulation results were com-pared with the results obtained by Gomes (2019). The existence of the central recirculation zone studied by Gomes (2019) was verified, for 𝐷/𝑑=5,4, and its closing point occurs at 𝑥=0,489 m, a quite different value from that obtai-ned by the author in 2019, 𝑥=0,190 m, due to the different swirl velocities used. Regarding the flow pattern, no trend was observed with the variation of the confine-ment ratio, due to the instability of the simulation imposed by the steady state. For the same reason, it was not possible to capture the incoming vortex for the different confinement ratios, present in the experimental studies by Camilo (2017) and Gomes (2019).
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Palavras-chave
escoamentos com rotação razão de confinamento vórtice ingressante zona de recirculação