Abstract: The turbulent drag is reduced on the surface of a body moving through a fluid by providing longitudinal channels in the surface, for example of an aircraft wing, which channels extend in parallel to the flow direction and which channels are interconnected with the boundary layer by a longitudinal gap communicating the channel with the boundary layer.

Abstract: An aircraft wing is equipped with at least one low compression fan which blows into a longitudinal flow channel extending lengthwise or spanwise of the wing and leading into air blowing nozzle arranged along the upper wing surface where the reduced pressure is largest for directly mixing the propulsion air jet or jets with the boundary layer air flowing along and adjacent to the upper wing surface. Both, the flow channel and the air blowing nozzles extend substantially along the entire length of the wing for increasing the resulting propulsion force and/or the resulting lift due to the mixing of the propulsion air jet with the boundary layer air directly in the boundary layer.