This work presents systematical investigations on the skin-friction drag reduction (DR) of turbulent channel flow subjected to spanwise wall oscillation using direct numerical simulation. Altogether 12 different oscillatory cases have been studied with a reference at Reτ = 200, varying the controlling parameters characterized by maximum wall velocity Wm+ and oscillation period T+. Some of the previously established facts have been reproduced by our analysis with a new focus on the phase-space dynamics of the near-wall streaks, on the basis of statistical data over entire oscillation periods and over phasewise variations. It is revealed that streamwise vortices are generated in the vicinity of oscillation walls, disrupting the formation of near-wall low-speed streaks. Although the overall turbulence is weakened, the Stokes layer is thicker within wall acceleration phases for larger Wm+, which causes the turbulence intensity to increase in the upper viscous sublayer. In addition, regarding the effect of T+, a long oscillation period promotes the formation of energetic near-wall structures, while for short T+, the streak-generation time scale preferentially restricts the growth of spanwise streaks. From a new vorticity-transport perspective of the Reynolds shear stress, our results further indicate that high drag-reducing phenomena are connected to the near-wall sweep events, and the shear stress variation is principally driven by the distortion of the spanwise transport of wall-normal vorticity, i.e., vortex tilting/stretching. The DR process is seen to be linked to the increase in enstrophy and turbulence-energy dissipation in the near-wall region.
Skip Nav Destination
Article navigation
December 2019
Research Article|
December 17 2019
Phase-space dynamics of near-wall streaks in wall-bounded turbulence with spanwise oscillation
Wenjun Yuan (袁文君)
;
Wenjun Yuan (袁文君)
1
Temasek Laboratories, National University of Singapore
, Engineering Drive 1, Singapore 117411, Singapore
2
Department of Mechanical Engineering, National University of Singapore
, Engineering Drive 1, Singapore 117575, Singapore
Search for other works by this author on:
Mengqi Zhang (张蒙齐);
Mengqi Zhang (张蒙齐)
a)
2
Department of Mechanical Engineering, National University of Singapore
, Engineering Drive 1, Singapore 117575, Singapore
Search for other works by this author on:
Yongdong Cui (崔永东)
;
Yongdong Cui (崔永东)
1
Temasek Laboratories, National University of Singapore
, Engineering Drive 1, Singapore 117411, Singapore
Search for other works by this author on:
Boo Cheong Khoo
Boo Cheong Khoo
1
Temasek Laboratories, National University of Singapore
, Engineering Drive 1, Singapore 117411, Singapore
2
Department of Mechanical Engineering, National University of Singapore
, Engineering Drive 1, Singapore 117575, Singapore
Search for other works by this author on:
a)
Electronic mail: mpezmq@nus.edu.sg
Note: This paper is part of the Special Topic, Papers Selected from the 8th International Symposium on Physics of Fluids.
Physics of Fluids 31, 125113 (2019)
Article history
Received:
October 03 2019
Accepted:
December 02 2019
Citation
Wenjun Yuan, Mengqi Zhang, Yongdong Cui, Boo Cheong Khoo; Phase-space dynamics of near-wall streaks in wall-bounded turbulence with spanwise oscillation. Physics of Fluids 1 December 2019; 31 (12): 125113. https://doi.org/10.1063/1.5130161
Download citation file:
Sign in
Don't already have an account? Register
Sign In
You could not be signed in. Please check your credentials and make sure you have an active account and try again.
Sign in via your Institution
Sign in via your InstitutionPay-Per-View Access
$40.00