期刊
JOURNAL OF FLUID MECHANICS
卷 681, 期 -, 页码 154-172出版社
CAMBRIDGE UNIV PRESS
DOI: 10.1017/jfm.2011.219
关键词
boundary layer control; drag reduction; turbulent boundary layers
资金
- Ministry of Education, Culture, Sports and Technology of Japan (MEXT) [20246036]
- Japan Aerospace Exploration Agency (JAXA)
- Keio University
- Center for Education and Research of Safe, Secure and Symbiotic System Design
- Grants-in-Aid for Scientific Research [20246036] Funding Source: KAKEN
Direct numerical simulation (DNS) of spatially developing turbulent boundary layer with uniform blowing (UB) or uniform suction (US) is performed aiming at skin friction drag reduction. The Reynolds number based on the free stream velocity and the 99% boundary layer thickness at the inlet is set to be 3000. A constant wall-normal velocity is applied on the wall in the range, -0.01U(infinity) <= V(ctr) <= 0.01U(infinity). The DNS results show that UB reduces the skin friction drag, while US increases it. The turbulent fluctuations exhibit the opposite trend: UB enhances the turbulence, while US suppresses it. Dynamical decomposition of the local skin friction coefficient c(f) using the identity equation (FIK identity) (Fukagata, Iwamoto & Kasagi, Phys. Fluids, vol. 14, 2002, pp. L73-L76) reveals that the mean convection term in UB case works as a strong drag reduction factor, while that in US case works as a strong drag augmentation factor: in both cases, the contribution of mean convection on the friction drag overwhelms the turbulent contribution. It is also found that the control efficiency of UB is much higher than that of the advanced active control methods proposed for channel flows.
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