On the flow past a circular cylinder from critical to super-critical Reynolds numbers: Wake topology and vortex shedding
Large-eddy simulations (LES) of the flow past a circular cylinder are used to investigate the flow topology and the vortex shedding process at Reynolds numbers Re=2.5×105-8.5×105Re=2.5×105-8.5×105. This range encompasses both the critical and super-critical regimes. As the flow enters the critical r...
| Autores: | , , , , |
|---|---|
| Tipo de recurso: | artículo |
| Fecha de publicación: | 2015 |
| País: | España |
| Institución: | Universitat Politècnica de Catalunya (UPC) |
| Repositorio: | UPCommons. Portal del coneixement obert de la UPC |
| Idioma: | inglés |
| OAI Identifier: | oai:upcommons.upc.edu:2117/85914 |
| Acceso en línea: | https://hdl.handle.net/2117/85914 https://dx.doi.org/10.1016/j.ijheatfluidflow.2015.05.009 |
| Access Level: | acceso abierto |
| Palabra clave: | Reynolds number Vortex shedding LES Critical and super-critical Reynolds numbers Coherent flow Wake topology Mecànica de fluids -- Models matemàtics Remolins (Mecànica de fluids) Àrees temàtiques de la UPC::Enginyeria mecànica::Mecànica de fluids |
| Sumario: | Large-eddy simulations (LES) of the flow past a circular cylinder are used to investigate the flow topology and the vortex shedding process at Reynolds numbers Re=2.5×105-8.5×105Re=2.5×105-8.5×105. This range encompasses both the critical and super-critical regimes. As the flow enters the critical regime, major changes occur which affect the flow configuration. Asymmetries in the flow are found in the critical regime, whereas the wake recovers its symmetry and stabilizes in the super-critical regime. Wake characteristic lengths are measured and compared between the different Reynolds numbers. It is shown that the super-critical regime is characterised by a plateau in the drag coefficient at about CD˜0.22CD˜0.22, and a quasi-stable wake which has a non-dimensional width of dw/D˜0.4dw/D˜0.4. The periodic nature of the flow is analysed by means of measurements of the unsteady drag and lift coefficients. Power spectra of the lift fluctuations are computed. Wake vortex shedding is found to occur for both regimes investigated, although a jump in frequencies is observed when the flow enters the super-critical regime. In this regime, non-dimensional vortex-shedding frequency is almost constant and equal to St=fvsD/Uref˜0.44St=fvsD/Uref˜0.44. The analysis also shows a steep decrease in the fluctuating lift when entering the super-critical regime. The combined analysis of both wake topology and vortex shedding complements the physical picture of a stable and highly coherent flow in the super-critical regime. |
|---|