Acoustic Reduction of Flow Separation

Airfoils produce more lift and less drag when the boundary layer is attached to the airfoil. With most aircraft there are combinations of airspeed and angle of attack where the boundary layer at least partially detaches from the airfoil. Reducing boundary layer detachment will increase lift and reduce drag. This will reduce fuel consumption saving money for the operator and improving control for the pilot. Two methods are known to improve boundary layer attachment: heating the air and supplying acoustic pressure at an airspeed and airfoil shape dependent frequency. Carbon nanotubes can be used to produce heating elements as thin as a layer of paint. Because they are thin they can be heated and cooled hundreds of times per second. This combination means that carbon nanotube heating elements can be thermoacoustic speakers to both heat the air stream and generate the appropriate acoustic frequency to maximize boundary zone attachment. All system components have been demonstrated individually achieving TRL 2. Phase I will demonstrate multifrequency sound generation on surfaces in a wind tunnel using nanotube heating elements, and achieving TRL 3. Phase II will include medium seals wind tunnel tests verifying the effects and achieving TRL 5.