THE WALL JET BENEATH A COUNTER-FLOWING STREAM.
Final technical rept. Sep 66-Mar 68,
VON KARMAN INST FOR FLUID DYNAMICS RHODE-SAINT-GENESE (BELGIUM)
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An experimental investigation of the flow arising from a wall jet beneath a counter-flowing stream was carried out. Such type of flow is related to the recirculation problem of jet lift VTOL aircraft flying or hovering in wind in ground proximity. Two different models were used in the program. The first one consisted of a circular cylinder with an elliptic nose shape whose axis was aligned to the main stream flow. An annular jet nozzle located at the rear of the model ejected air tangentially to the cylinder in the opposite direction to the main stream. The second model consisted of a flat plate with side walls. The jet nozzle was located along the trailing edge of the plate and the air was ejected tangetially to the surface of the plate toward the leading edge. The flow configuration obtained with both models showed a deep penetration of the jet in the main stream when the jet velocity was large compared to the free stream producing a large separation bubble with a strong vortex motion inside. Author