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Turbulent boundary layer (TBL) exists in numerous engineering applications, such as commercial airplanes, high-speed railway and oil pipes. The skin-friction drag in a TBL is usually the main source of power consumption. Even a modest reduction in skin-friction drag will lead to tremendous saving on power consumption and costs. Skin-friction drag is closely associated with quasi-streamwise vortices (QSVs), which occur mostly in the buffer layer, immediately above the large wall shear stress (WSS) sublayer. One approach for drag reduction is through the plasma-induced large-scale streamwise vortices. A spatial-averaged drag reduction of 26% over an area of 0.1 m × 0.2 m is achieved downstream of the actuators at Reθ = 1450. Flow visualization near the wall and analyses of hotwire and PIV data with and without control point to a pronounced change in the coherent structures in the TBL under control.

             

 



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PIV-measured time-averaged vorticity field in y-z plane produced by three different DBD plasma actuator arrays.

 

Typical photograph of the smoke-wire flow visualization of instantaneous flow structure at y+ = 24 for (a) natural and (b) manipulated flow with control.