Reattachment of a Separation Cell using a Discrete Jet Array

The flow topology and turbulent structure of a separation cell formed in the adverse pressure gradient over a nominally 2-D surface, similar to forward stall cells over airfoils, are investigated experimentally in the absence and presence of fluidic control.  Actuation is effected by a spanwise array of surface-tangential, fluidically oscillating jets located upstream of the cell formation.  The effects of the actuation on the streamwise evolution of the cell structure are assessed using stereo particle image velocimetry in several streamwise-normal planes.  The evolution of concentrations of streamwise vorticity is assessed with specific emphasis on its turbulent organization within the cell’s global topology by the presence of the jet actuation.  It is shown that flow reattachment between the cell’s bounding outboard edge vortices is facilitated by the formation of a spanwise array of segmented reattachment cells that scale with the actuation jets and are each bounded by pairs of vorticity concentrations with predominantly opposite sense.

Supported by VLRCOE at Georgia Tech.