Large-Scale Streamwise Vortices in Turbulent Channel Flow Induced by Active Wall Actuations

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

Abstract

© 2017, Springer Science+Business Media B.V., part of Springer Nature. Direct numerical simulations of turbulent flow in a plane channel using spanwise alternatively distributed strips (SADS) are performed to investigate the characteristics of large-scale streamwise vortices (LSSVs) induced by small-scale active wall actuations, and their role in suppressing flow separation. SADS control is obtained by alternatively applying out-of-phase control (OPC) and in-phase control (IPC) to the wall-normal velocity component of the lower channel wall, in the spanwise direction. Besides the non-controlled channel flow simulated as a reference, four controlled cases with 1, 2, 3 and 4 pairs of OPC/IPC strips are studied at M = 0.2 and Re = 6,000, based on the bulk velocity and the channel half height. The case with 2 pairs of strips, whose width is Δz+ = 264 based on the friction velocity of the non-controlled case, is the most effective in terms of generating large-scale motions. It is also found that the OPC (resp. IPC) strips suppress (resp. enhance) the coherent structures and that leads to the creation of a vertical shear layer, which is responsible for the LSSVs presence. They are in a statistically steady state and their cores are located between two neighbouring OPC and IPC strips. These motions contribute significantly to the momentum transport in the wall-normal and spanwise directions showing potential for flow separation suppression.

• Journal Article Type: Article
• Acceptance Date: Nov 28, 2017
• Online Publication Date: Nov 29, 2017
• Publication Date: Apr 1, 2018
• Deposit Date: Jan 3, 2018
• Publicly Available Date: Nov 29, 2018
• Journal: Flow, Turbulence and Combustion
• Print ISSN: 1386-6184
• Electronic ISSN: 1573-1987
• Publisher: Springer Verlag
• Peer Reviewed: Peer Reviewed
• Volume: 100
• Issue: 3
• Pages: 651-673
• DOI: https://doi.org/10.1007/s10494-017-9871-5
• Public URL: https://uwe-repository.worktribe.com/output/902888
• Publisher URL: http://dx.doi.org/10.1007/s10494-017-9871-5
• Additional Information: Additional Information : This is a post-peer-review, pre-copyedit version of an article published in Flow, Turbulence and Combustion. The final authenticated version is available online at: http://dx.doi.org/10.1007/s10494-017-9871-5
• Contract Date: Jan 3, 2018