

Article
On largescale friction control in turbulent wall flow in low Reynolds number channels
Authors: 
Canton, J.C., Örlü, R., Chin, C., Hutchins, N., Monty, J., Schlatter, P. 
Document Type: 
Article 
Pubstate: 
Published 
Journal: 
Flow, Turbulence and Combustion 
Volume: 
97
811827 
Year: 
2016 
AbstractThe present study reconsiders the control scheme proposed by Schoppa \& Hussain (Phys. Fluids 10, 10491051 1998), using a new set of numerical simulations. The computations are performed in a turbulent channel at friction Reynolds numbers of 104 (the value employed in the original study) and 180. In particular, the aim is to better characterise the physics of the control as well as to investigate the optimal parameters. The former purpose lead to a redesign of the control strategy: moving from a numerical imposition of the mean flow to the application of a volume force. A comparison between the two is presented. Results show that the original method only gave rise to transient drag reduction. The forcing method, on the other hand, leads to sustained drag reduction, and thus shows the superiority of the forcing approach for all wavelengths investigated. A clear maximum efficiency in drag reduction is reached for the case with a viscousscaled spanwise wavelength of the vortices of 1200, which yields a drag reduction of 18 \%, as compared to the smaller wavelength of 400 suggested as the most efficient vortex in Schoppa \& Hussain. Various turbulence statistics are considered, in an effort to elucidate the causes of the dragreducing effect. For instance, a region of negative production was found, which is quite unusual for developed turbulent channel flow.
dx.doi.org/10.1007/s1049401697238

