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Article
Flow separation control behind a cylindrical bump using dielectric-barrier-discharge vortex generator plasma actuators
| Authors: |
Vernet, J., Örlü, R., Alfredsson, P.H. |
| Document Type: |
Article |
| Pubstate: |
Published |
| Journal: |
J. Fluid Mech. |
| Volume: |
835
852–879 |
| Year: |
2018 |
AbstractDielectric-barrier-discharge plasma actuators are arranged to produce counter-rotating streamwise vortices to control flow separation on a cylindrical bump on a flat plate that is approached by a turbulent boundary layer. The control was tested for different free-stream velocities and actuation driving voltages. The recirculation area downstream of the bump was reduced by the actuation for velocities up to 15m/s at the highest voltage achievable of the present set-up. However, the flow shows a bi-modality, the nominal two-dimensional wake flow is shown to consist of large-scale streamwise vortices, which are energised by the actuation until a phenomenon of lock-on of these vortices occurs at sufficiently high driving voltages. The wavelength of the actuation is half that of the large-scale vortices. The lock-on shifts sometimes, i.e. the large streamwise vortices centre switch spanwise location, explaining the bi-modality in the flow. The details of the bi-modality are further investigated by conditional averaging and proper orthogonal decomposition.
https://doi.org/10.1017/jfm.2017.773
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