Active control of turbulence for drag reduction based on the detection of near-waU streamwise vortices by wall information

The spatial relations between the measurable wall quantities(streamwise shear stress τwx, spanwise shear stress τwz, and pressure fluctuation p w) and the near-wall streamwise vortices(NWSV) are investigated via direct numerical simulation(DNS) databases of fully developed turbulent channel flow at a low Reynolds number. In the standard turbulent channel flow, the results show that all the wall measurable variables are closely associated with the NWSV.Butafterapplyingastochasticinterference,therelationbased on τwx breaks down while the correlations based on p wandτwz are still robust. Hence, two wall flow quantities based on p wand τwz are proposed to detect the NWSV. As an application, two new control schemes are developed to suppress the near-wall vortical structures using the actuation of wall blowing/suction and obtain 16 % and 11 % drag reduction,respectively.