Direct numerical simulation of spatially developing turbulent boundary layers with uniform blowing or suction

• Published in: Journal of fluid mechanics 2011-08, Vol.681, p.154-172
• Main Authors: KAMETANI, YUKINORI, FUKAGATA, KOJI
• Format: Article
• Language: English
• Subjects: Blowing; Boundary layer; Boundary layer and shear turbulence; Boundary layers; Computational fluid dynamics; Convection; Drag; Drag reduction; Exact sciences and technology; Flows in ducts, channels, nozzles, and conduits; Fluid dynamics; Fluid flow; Fluid mechanics; Friction; Fundamental areas of phenomenology (including applications); Numerical analysis; Physics; Reynolds number; Skin friction; Turbulence; Turbulence control; Turbulent flow; Turbulent flows, convection, and heat transfer
• ISSN: 0022-1120; 1469-7645
• DOI: 10.1017/jfm.2011.219

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∞ ≤ Vctr ≤ 0.01U∞. 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 cf 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.