US Patent 8016567 Separation resistant aerodynamic article

An airfoil disclosed herein comprises a pressure surface 42 exposed to a stream of fluid, a suction surface 40 exposed to the stream of fluid and a passage 56 extending from a passage intake end 60 to a passage discharge end 66. The intake end has an intake opening 62 penetrating the pressure surface for extracting fluid from the fluid stream. The discharge end has a discharge opening 68 penetrating the suction surface upstream of a natural separation point 52. The discharge end is configured to inject the extracted fluid into the fluid stream at a jet angle whose components include at least one of a nonzero streamwise angle α in a prescribed angular range and a nonzero cross-stream angle β.