Global response of laminar flow separation to local flow perturbations (review)

In the present paper, we summarize our experimental data on flow separation control on wings at low subsonic velocities. The focus is on the reduction of the separation region by stationary and nonstationary controlled flow perturbations. Wind-tunnel data obtained for test models of different aspect ratios prove that the entire separated flow can be modified by forcing its narrow parts much smaller in size than the transverse extent of the separation region. Such an approach to flow control at laminar separation comes from non-local interaction of the large-scale flow structure with spatially concentrated disturbances.