High performance airfoil using co-flow jet flow control

A novel airfoil flow control concept, co-flow jet (CFJ) airfoil, is developed in our research and its high performance is proved in wind tunnel tests. The CFJ airfoil simultaneously achieves three effects in a very significant manner: 1) lift enhancement, 2) drag reduction or thrust generation (negative drag), 3) stall margin increase. The fundamental mechanism of the CFJ airfoil is that the high energy jet transfers the energy to the main flow via turbulent mixing under severe adverse pressure gradient. The airfoil main flow is hence able to overcome the adverse pressure gradient and remains attached. At the same time, the high speed jet induces a large circulation and hence a high lift is generated. More study of the fundamental physics of the co-flow jet mixing is under way.

The coflow jet airfoil concept studied in this research appears to have the following advantages: 1) Very effective to enhance lift and suppress separation; 2) Drastically reduce drag and can achieve very high L/D at low AoA(cruise), and very high lift and drag at high AoA(take off and landing); 3) Significantly increase AoA operating range and stall margin; 4) Have small penalty to the propulsion system; 5) Can be applied to any airfoil, thick or thin; 6) Can be used for entire flying mission instead of only take off and landing; 7) Easy implementation.

The above advantages of the CFJ airfoil may derive the following superior aircraft performances: 1) Extremely short distance for take off and landing; 2) Supersonic aircraft to have small wing size matching cruise need, but also have high subsonic performance (e.g. high lift low drag at M<1); 3) High maneuverability, high safety and fast acceleration military aircraft; 4) Very economic fuel consumption; 5) Small wing span for easy storage, light weight and reduced skin friction and form drag; 6) Low noise due to no high lift flap system and weakened wake mixing.

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