Large-scale secondary vortices in the turbulent channel flow induced by active wall actuations

Ni, Weidan; Lu, Lipeng; Fang, Jian; Yao, Yufeng; Moulinec, Charles

Abstract

Direct numerical simulations (DNS) of the turbulent channel flow with spanwise alternatively distributed out-of-phase (OP) and in-phase (IP) wall actuations strips (SADS) are conducted to investigate the characteristics of the large-scale streamwise vortex (LSSV) induced by the small-scale active wall actuations. DNS of an unperturbed channel flow is first validated against the DNS data of Moser et al. [1]. SADS is realized by alternatively arranging OP [2] and IP wall fluctuations on the bottom wall of the channel. As expected, the turbulent coherent structures are alternatively enhanced and suppressed by SADS. Large-scale low-speed region can be observed above the OP strips and the low-speed region looks as a kind of steady streak structure. Reynolds shear stress is increased both in the near-wall region above the IP strips and close to the central part of the channel beyond the OP regions. This is caused by the ejection of the large-scale counter-rotating streamwise vortices generated between IP and OP strips. Therefore, the LSSV generated by the current small-scale wall actuation presents a strong ability in enhancing turbulence momentum transport and mixing, which gives a great promise in suppressing flow separation.

• Presentation Conference Type: Conference Paper (unpublished)
• Conference Name: The Seventh International Symposium on Physics of Fluids (ISPF7)
• Start Date: Jun 5, 2017
• End Date: Jun 8, 2017
• Acceptance Date: Jun 5, 2017
• Publication Date: Jun 8, 2017
• Peer Reviewed: Peer Reviewed
• Public URL: https://uwe-repository.worktribe.com/output/886266
• Additional Information: Title of Conference or Conference Proceedings : The Seventh International Symposium on Physics of Fluids (ISPF7)