Manipulating the flow over a circular cylinder with control rods.
Autor(a) principal: | |
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Data de Publicação: | 2021 |
Tipo de documento: | Tese |
Idioma: | eng |
Título da fonte: | Biblioteca Digital de Teses e Dissertações da USP |
Texto Completo: | https://www.teses.usp.br/teses/disponiveis/3/3150/tde-14022022-105402/ |
Resumo: | The flow past a circular cylinder with control rods at moderate values of Reynolds number is experimentally investigated in this work. The flow topology depends on many parameters, such as Reynolds number (Re), the ratio between the diameter of the cylinders (d/D), number and position of the rods. Preliminary experiments on the sensitivity of fluid forces have shown that the rods position is the most relevant among all the parameters tested. The hydrodynamic forces suffer the greatest variation when the rod is placed close to the shear layers or the cylinders surface. Detailed investigation of the wake with one-rod using fixed values of Re = 20, 000, and d/D = 0.1 has shown that the wake developed three distinct states, depending on the rods angular position . State I is characterised by two distinct vortex streets, downstream of the cylinder and rod, respectively. State II is characterised by a strong jet between the cylinder and the rod and a late separation due to Coanda effect. And in State III the rod acts in the recirculation region, with a relatively lower influence in the flow compared to the other states. In addition, a bi-stable case was observed between the states II and III, with no clear switching frequency between the states and very sensitive to the rods position. Adding a second and symmetrical rod to the system turns the mean flow symmetric for States I and III, whereas State II shows an asymmetric mean wake due to a bi-stable behaviour induced by the imbalance of the jets in the near wake. A transitional case was observed between State I and II, with a type of separation not observed for one-rod cases, which showed a reduction of 90% in the fluctuating lift force.The position of the separation point varied significantly for States I and II compared to that of a bare cylinder. It prompted a significant impact on the hydrodynamic forces acting on the cylinder. The greatest reductions of the mean drag force were observed for State II cases with two-rod: 20% for the combined system and 30% for the main cylinder, both with respect to the bare cylinder case. |
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Manipulating the flow over a circular cylinder with control rods.Manipulação do escoamento ao redor de um cilindro com hastes de controle.Dinâmica dos fluidosEscoamento (Controle)Escoamento ao redor de corpos rombudosExperimental Ffuid mechanicsFlow around bluff bodiesFlow controlFluid dynamicMecânica dos FluidosThe flow past a circular cylinder with control rods at moderate values of Reynolds number is experimentally investigated in this work. The flow topology depends on many parameters, such as Reynolds number (Re), the ratio between the diameter of the cylinders (d/D), number and position of the rods. Preliminary experiments on the sensitivity of fluid forces have shown that the rods position is the most relevant among all the parameters tested. The hydrodynamic forces suffer the greatest variation when the rod is placed close to the shear layers or the cylinders surface. Detailed investigation of the wake with one-rod using fixed values of Re = 20, 000, and d/D = 0.1 has shown that the wake developed three distinct states, depending on the rods angular position . State I is characterised by two distinct vortex streets, downstream of the cylinder and rod, respectively. State II is characterised by a strong jet between the cylinder and the rod and a late separation due to Coanda effect. And in State III the rod acts in the recirculation region, with a relatively lower influence in the flow compared to the other states. In addition, a bi-stable case was observed between the states II and III, with no clear switching frequency between the states and very sensitive to the rods position. Adding a second and symmetrical rod to the system turns the mean flow symmetric for States I and III, whereas State II shows an asymmetric mean wake due to a bi-stable behaviour induced by the imbalance of the jets in the near wake. A transitional case was observed between State I and II, with a type of separation not observed for one-rod cases, which showed a reduction of 90% in the fluctuating lift force.The position of the separation point varied significantly for States I and II compared to that of a bare cylinder. It prompted a significant impact on the hydrodynamic forces acting on the cylinder. The greatest reductions of the mean drag force were observed for State II cases with two-rod: 20% for the combined system and 30% for the main cylinder, both with respect to the bare cylinder case.O escoamento ao redor de cilindros com hastes de controle para valores moderados do número de Reynolds investigado neste trabalho. A topologia do escoamento depende de vários parâmetros, dentre os quais o número de Reynolds (Re), a razão entre os diâmetros dos cilindros (d/D), número e posição das hastes. Experimentos preliminares para avaliar a sensibilidade das forças hidrodinâmicas mostraram que a posição das hastes o parâmetro mais relevante dentre os avaliados. As forças sofrem maiores variações quando a haste está próxima ou da camada cisalhante ou da parede do cilindro. Investigações detalhadas com apenas uma haste de controle e valores fixos de Re = 20.000 e d/D = 0, 1 mostraram que a esteira desenvolve três estados distintos, dependendo da posição angular da haste ?. O estado I caracterizado pela presença de duas esteiras de vórtices distintas, a jusante do cilindro e da haste, respectivamente. O estado II caracterizado por um intenso jato entre o cilindro e a haste e uma separação tardia provocada pelo efeito Coandã. No estado III a haste est na região de recirculação, afetando menos o escoamento em comparação com os outros estados. Adicionalmente, um caso biestável foi observado entre os estados II e III, sem uma clara frequência de trânsito entre eles e bastante sensível a posição das hastes. A adio de uma segunda haste, simétrica a primeira, torna o escoamento médio simétrico nos estados I e III, enquanto que o estado II apresenta uma esteira média assimétrica devido a um comportamento biestável, induzido pelo desbalanço da intensidade dos dois jatos na esteira próxima. Um caso transicional entre os estados I e II foi observado, com um tipo de separação no verificado nos casos com uma haste, mostrando uma redução de 90% da flutuação da fora de sustentação. A posição do ponto de separação variou significantemente nos estados I e II em relação ao cilindro liso, especialmente nos estados I e II. Esta variação provocou um grande impacto nas forças hidrodinâmicas. As maiores recues na fora média de arrasto foram observadas no estado II com duas hastes: 20% para o sistema completo e 30% considerando somente o cilindro principal, ambos em relação ao caso do cilindro liso.Biblioteca Digitais de Teses e Dissertações da USPAssi, Gustavo Roque da SilvaCicolin, Murilo Marangon2021-08-06info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/doctoralThesisapplication/pdfhttps://www.teses.usp.br/teses/disponiveis/3/3150/tde-14022022-105402/reponame:Biblioteca Digital de Teses e Dissertações da USPinstname:Universidade de São Paulo (USP)instacron:USPLiberar o conteúdo para acesso público.info:eu-repo/semantics/openAccesseng2022-02-21T13:10:02Zoai:teses.usp.br:tde-14022022-105402Biblioteca Digital de Teses e Dissertaçõeshttp://www.teses.usp.br/PUBhttp://www.teses.usp.br/cgi-bin/mtd2br.plvirginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.bropendoar:27212022-02-21T13:10:02Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP)false |
dc.title.none.fl_str_mv |
Manipulating the flow over a circular cylinder with control rods. Manipulação do escoamento ao redor de um cilindro com hastes de controle. |
title |
Manipulating the flow over a circular cylinder with control rods. |
spellingShingle |
Manipulating the flow over a circular cylinder with control rods. Cicolin, Murilo Marangon Dinâmica dos fluidos Escoamento (Controle) Escoamento ao redor de corpos rombudos Experimental Ffuid mechanics Flow around bluff bodies Flow control Fluid dynamic Mecânica dos Fluidos |
title_short |
Manipulating the flow over a circular cylinder with control rods. |
title_full |
Manipulating the flow over a circular cylinder with control rods. |
title_fullStr |
Manipulating the flow over a circular cylinder with control rods. |
title_full_unstemmed |
Manipulating the flow over a circular cylinder with control rods. |
title_sort |
Manipulating the flow over a circular cylinder with control rods. |
author |
Cicolin, Murilo Marangon |
author_facet |
Cicolin, Murilo Marangon |
author_role |
author |
dc.contributor.none.fl_str_mv |
Assi, Gustavo Roque da Silva |
dc.contributor.author.fl_str_mv |
Cicolin, Murilo Marangon |
dc.subject.por.fl_str_mv |
Dinâmica dos fluidos Escoamento (Controle) Escoamento ao redor de corpos rombudos Experimental Ffuid mechanics Flow around bluff bodies Flow control Fluid dynamic Mecânica dos Fluidos |
topic |
Dinâmica dos fluidos Escoamento (Controle) Escoamento ao redor de corpos rombudos Experimental Ffuid mechanics Flow around bluff bodies Flow control Fluid dynamic Mecânica dos Fluidos |
description |
The flow past a circular cylinder with control rods at moderate values of Reynolds number is experimentally investigated in this work. The flow topology depends on many parameters, such as Reynolds number (Re), the ratio between the diameter of the cylinders (d/D), number and position of the rods. Preliminary experiments on the sensitivity of fluid forces have shown that the rods position is the most relevant among all the parameters tested. The hydrodynamic forces suffer the greatest variation when the rod is placed close to the shear layers or the cylinders surface. Detailed investigation of the wake with one-rod using fixed values of Re = 20, 000, and d/D = 0.1 has shown that the wake developed three distinct states, depending on the rods angular position . State I is characterised by two distinct vortex streets, downstream of the cylinder and rod, respectively. State II is characterised by a strong jet between the cylinder and the rod and a late separation due to Coanda effect. And in State III the rod acts in the recirculation region, with a relatively lower influence in the flow compared to the other states. In addition, a bi-stable case was observed between the states II and III, with no clear switching frequency between the states and very sensitive to the rods position. Adding a second and symmetrical rod to the system turns the mean flow symmetric for States I and III, whereas State II shows an asymmetric mean wake due to a bi-stable behaviour induced by the imbalance of the jets in the near wake. A transitional case was observed between State I and II, with a type of separation not observed for one-rod cases, which showed a reduction of 90% in the fluctuating lift force.The position of the separation point varied significantly for States I and II compared to that of a bare cylinder. It prompted a significant impact on the hydrodynamic forces acting on the cylinder. The greatest reductions of the mean drag force were observed for State II cases with two-rod: 20% for the combined system and 30% for the main cylinder, both with respect to the bare cylinder case. |
publishDate |
2021 |
dc.date.none.fl_str_mv |
2021-08-06 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/doctoralThesis |
format |
doctoralThesis |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
https://www.teses.usp.br/teses/disponiveis/3/3150/tde-14022022-105402/ |
url |
https://www.teses.usp.br/teses/disponiveis/3/3150/tde-14022022-105402/ |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
|
dc.rights.driver.fl_str_mv |
Liberar o conteúdo para acesso público. info:eu-repo/semantics/openAccess |
rights_invalid_str_mv |
Liberar o conteúdo para acesso público. |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.coverage.none.fl_str_mv |
|
dc.publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
publisher.none.fl_str_mv |
Biblioteca Digitais de Teses e Dissertações da USP |
dc.source.none.fl_str_mv |
reponame:Biblioteca Digital de Teses e Dissertações da USP instname:Universidade de São Paulo (USP) instacron:USP |
instname_str |
Universidade de São Paulo (USP) |
instacron_str |
USP |
institution |
USP |
reponame_str |
Biblioteca Digital de Teses e Dissertações da USP |
collection |
Biblioteca Digital de Teses e Dissertações da USP |
repository.name.fl_str_mv |
Biblioteca Digital de Teses e Dissertações da USP - Universidade de São Paulo (USP) |
repository.mail.fl_str_mv |
virginia@if.usp.br|| atendimento@aguia.usp.br||virginia@if.usp.br |
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1809090702598995968 |