Large-scale coherent motions in turbulent boundary layers under an adverse pressure gradient up to flow separation
| Autor: | Christian J. Kähler, Felix Eich |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Fluid Flow and Transfer Processes
Physics Turbulence Mechanical Engineering Reynolds number 02 engineering and technology Mechanics Condensed Matter Physics Boundary layer thickness 01 natural sciences 010305 fluids & plasmas Physics::Fluid Dynamics Adverse pressure gradient Boundary layer Flow separation symbols.namesake 020303 mechanical engineering & transports 0203 mechanical engineering Flow (mathematics) 0103 physical sciences symbols Mean flow |
| Zdroj: | International Journal of Heat and Fluid Flow. 85:108645 |
| ISSN: | 0142-727X |
| DOI: | 10.1016/j.ijheatfluidflow.2020.108645 |
| Popis: | A turbulent boundary layer under the impact of a strong adverse pressure gradient up to flow separation is investigated experimentally at Reynolds numbers up to Re τ = 12 , 000 , with the aim to analyse and characterise the interaction between large-scale coherent turbulent structures and a separated flow region. It is shown that the dynamics of the separation line in space and time are strongly modulated by the low frequency large-scale flow motions. Using a conditional comparison of mean flow parameters, it is shown that high-momentum large-scale motions are able to shift the point of separation downstream while the opposite is true for low-momentum large-scale motions. This interaction has a significant impact on the temporal dynamics of the separation line. The spatial frequencies observable along the line of separation on the other hand are determined by the spanwise arrangement of high and low-momentum large-scale motions. Finally, it is demonstrated that the separated region does not have a major influence on the mean boundary layer thickness in contrast to the mean flow velocity and spatial scales of coherent structures which are visibly influenced in the vicinity of the separated region. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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