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Flow separation control over a rounded ramp with spanwise alternating wall actuation

Ni, Weidan; Lu, Lipeng; Fang, Jian; Moulinec, Charles; Emerson, David R.; Yao, Yufeng

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Weidan Ni

Lipeng Lu

Jian Fang

Charles Moulinec

David R. Emerson

Yufeng Yao
Professor in Aerospace Engineering


An implicit large-eddy simulation is carried out to study turbulent boundary-layer separation from a backward-facing rounded ramp with active wall actuation control. This method, called spanwise alternating distributed strips control, is imposed onto the flat plate surface upstream of a rounded ramp by alternatively applying out-of-phase control and in-phase control to the wall-normal velocity component in the spanwise direction. As a result, the local turbulence intensity is alternatively suppressed and enhanced, leading to the creation of vertical shear-layers, which is responsible for the presence of large-scale streamwise vortices. These vortices exert a predominant influence on the suppression of the flow separation. The interaction between the large-scale vortices and the downstream recirculation zone and free shear-layer is studied by examining flow statistics. It is found that in comparison with the non-controlled case the flow separation is delayed, the reattachment point is shifted upstream, and the length of the mean recirculation zone is reduced up to 8.49%. The optimal control case is achieved with narrow in-phase control strips. An in-depth analysis shows that the delay of the flow separation is attributed to the activation of the near-wall turbulence by the in-phase control strips and the improvement of the reattachment location is mainly due to the large-scale streamwise vortices, which enhance the momentum transport between the main flow and separated region.


Ni, W., Lu, L., Fang, J., Moulinec, C., Emerson, D. R., & Yao, Y. (2019). Flow separation control over a rounded ramp with spanwise alternating wall actuation. Physics of Fluids, 31(1), 015101.

Journal Article Type Article
Acceptance Date Dec 7, 2018
Online Publication Date Jan 4, 2019
Publication Date Jan 1, 2019
Deposit Date Jan 15, 2019
Publicly Available Date Jan 15, 2019
Journal Physics of Fluids
Print ISSN 1070-6631
Electronic ISSN 1089-7666
Publisher AIP Publishing
Peer Reviewed Peer Reviewed
Volume 31
Issue 1
Pages 015101
Public URL
Publisher URL


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