A method to control flow separation over an airfoil, turbine blade or compressor blade includes providing an airfoil having a body with an upper surface and a lower surface that extend from a leading edge to a trailing edge; providing a flow separation control device having a plurality of openings on the upper surface of the body and a plurality of capillary tubes in gaseous communication with the plurality of openings; and injecting gas through the plurality of capillary tubes into a portion of the airstream passing over the uppers surface of the body.