Systems and methods for attenuation of noise and wakes produced by aircraft
Systems and methods for reducing the trailing vortices and lowering the noise produced by the side edges of aircraft flight control surfaces, tips of wings and winglets, and tips of rotor blades. A noise-reducing, wake-alleviating device is disclosed which incorporates an actuator and one or more air-ejecting slot-shaped openings coupled to that actuator and located on the upper and/or lower surfaces and/or the side edges of an aircraft flight control surface or the tip of a wing, winglet or blade. The actuation mechanism produces sets of small and fast-moving air jets that traverse the openings in the general streamwise direction. The actuation destabilizes the flap vortex structure, resulting in reduced intensity of trailing vortices and lower airplane noise.
1. A method of attenuating noise generated by an aerodynamic element during flight of a vehicle, comprising:
(a) forming a slot on or near a side edge of an aerodynamic element having upper and lower surfaces, which slot will be generally aligned with a streamwise direction during flight;
(b) ejecting air out of the slot in the form of an air jet which moves along at least a portion of the length of the slot in a stream wise direction for a distance that is greater than a width of the air jet; and
(c) extinguishing the air jet when it reaches a termination point.
2. The method as recited in claim 1 , wherein step (b) comprises rotating a cylinder having an interior duct and a helical slot in fluid communication with the interior duct.
3. The method as recited in claim 1 , comprising repeating steps (b) and (c) such that a multiplicity of air jets traverse the slot in succession.
4. The method as recited in claim 1 , wherein step (b) comprises rotating a cylinder having an interior duct and a multiplicity of openings in fluid communication with the interior duct, each opening of the multiplicity of openings being in fluid communication with the slot once per revolution of the rotating cylinder.
5. The method as recited in claim 1 , comprising repeating steps (a), (b) and (c) for two different slots, one slot being located on one of the upper surface, lower surface and side edge, and a second slot being located on one of the upper surface, lower surface and side edge on which the first slot is not located.
6. The method as recited in claim 1 , wherein step (b) comprises rotating a cylinder having an interior duct and a helical slot in fluid communication with the interior duct, the helical slot being in continuous fluid communication with the slot formed in the aerodynamic element during revolution of the rotating cylinder.
7. A method of attenuating noise generated by an aerodynamic element during flight of a vehicle, comprising:
(a) forming a slot on or near a side edge of an aerodynamic element having upper and lower surfaces, which slot will be generally aligned with a streamwise direction during flight;
(b) ejecting air out of the slot in the form of a plurality of successively initiated air jets which traverse respective portions of a length of the slot concurrently, each successively initiated air jet traversing a length of the slot in a streamwise direction during partially overlapping time intervals; and
(c) extinguishing each air jet in succession when it reaches a termination point.
8. The method as recited in claim 7 , wherein step (b) comprises rotating a cylinder having an interior duct and a plurality of helical slots in fluid communication with the interior duct, each helical slot being in continuous fluid communication with the slot formed in the aerodynamic element during revolution of the rotating cylinder.
9. A method of attenuating noise generated by an aerodynamic element during flight of a vehicle, comprising the following steps performed prior to flight:
(a) forming a slot on or near a side edge of an aerodynamic element having upper and lower surfaces, which slot will be generally aligned with a streamwise direction during flight;
(b) forming a cylinder having an interior duct and a multiplicity of slots or apertures in fluid communication with the interior duct; and
(c) arranging the cylinder so that it is rotatable about its axis and so that each slot or aperture will be in fluid communication with the slot once during each revolution of the cylinder, and
comprising the following steps performed during flight:
(d) supplying pressurized air to the interior duct of the cylinder; and
(e) rotating the cylinder while pressurized air is being supplied,
wherein the slots or apertures are arranged so that air is intermittently ejected out of the slot during step (e) in the form of successive pluralities of concurrently initiated air jets.