Finite bluff body wake control using boundary layer triggered transition

• Autor(a) principal: Tiago Barbosa de Araújo
• Data de Publicação: 2012
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações do ITA
• Texto Completo: http://www.bd.bibl.ita.br/tde_busca/arquivo.php?codArquivo=2177
• topic: Corpos rombudos; Escoamento tridimensional; Cilindros circulares; Mecânica dos fluidos; Física

The bluff body flow is often related to engeneering problems and because of it this kind of flow is largely studied. Most of the laboratory works are done with two-dimensinal (2D) or infinite flow, however the flows of industrial applications are normally three-dimensional (3D) and includes complex interactions among its shear layers. In this work, the flow over two finite circular cylinders mounted on a flat plate is studied. Passive flow control is applied on the finite cylinders, using single tripwire located at different azimuthal positions, is experimentally investigated. The influence of this disturbance on the near wake flow structures, vortex shedding characteristics and surface pressure are presented for two different aspect ratios, 3 and 6. Abrupt variations on mean measured parameters are observed for both aspect ratios and a critical angular position is found. Furthermore the changes due to aspect ratio variation are pointed out, specially on the near wake flow fields obtained by PIV measurements which are influenced by the inflow induced by the tip vortices. Drag and pressure fluctuations reduction as well as mean lift are observed. Further results suggest that the near wake characteristics are close to those of the infinite circular cylinder (2D) for the larger aspect ratio and that there exist a bi-stable regime of the flow in the presence of the tripwire.