A rectangular duct having a gas flow therethrough wherein there is a tendency for the gas flow to separate from a wall of the duct having an aerodynamic nozzle positioned adjacent the wall that results in a downwash of gas which deters separation. In a duct wherein a plurality of nozzles provide a primary flow of air in a rectangular duct wherein ambient air is entrained and mixed with the primary air, the tip vortices from the aerodynamic nozzles positioned adjacent the duct end walls enhance the mixing and cancel the vortices naturally forming at the juncture of the side walls and the end walls.