One embodiment is an apparatus including an airfoil-shaped body; and a chordwise variable vortex generation system associated with the airfoil-shaped body, the chordwise variable vortex generation system controlling a deployment of at least one vortex generator on a surface of the airfoil-shaped body, wherein the deployment of the at least one vortex generator is dependent on a current angle of attack of the airfoil-shaped body. In some embodiments, the chordwise variable vortex generation system includes an actuator for controlling a location of the deployment of the at least one vortex generator responsive to a control signal indicative of the current angle of attack of the airfoil-shaped body. In certain embodiments, the surface of the airfoil-shaped body is a top surface of the airfoil-shaped body. In some embodiments, the airfoil-shaped body is an aircraft wing.

This disclosure relates to a method and resulting apparatus of applying a riblet sheet comprising a riblet film layer and a riblet liner layer on an airfoil surface. The method comprises applying the riblet film layer of the riblet sheet over the airfoil surface, peeling back at least a portion of the riblet liner layer from the riblet film layer to expose a portion of the riblet film layer, applying a attaching hardware or a non-textured surface film over at least a portion the riblet film layer portion; and applying the peeled back portion of the riblet liner layer over a portion of the attaching hardware.

An inset configured for use in a rotor blade is provided including a body having a shape generally complementary to a hole formed in the rotor blade. An opening extends between a first surface and a second surface of the body. The opening is configured to provide a fluid flow path between an interior and an exterior of the rotor blade.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Systems, methods, and apparatus may actively adjust the position and/or configuration of one or more propeller blades of a propulsion mechanism to generate different sounds and/or lifting forces from the propulsion mechanism.

A rotor system is provided in one example embodiment and may include a first pair of rotor blades comprising a first pitch and a first diameter; and a second pair of rotor blades comprising a second pitch and a second diameter, wherein the first pitch of the first pair of rotor blades and the second pitch of the second pair of rotor blades are different.

An aerial vehicle is provided including rotor units connected to the aerial vehicle, and a control system configured to operate at least one of the rotor units. The rotor unit includes rotor blades, wherein each rotor blade includes a surface area, and wherein an asymmetric parameter is defined, at least in part, by the relationship between the surface areas of the rotor blades. The value of the asymmetric parameter is selected such that the operation of the rotor unit: (i) moves the rotor blades such that each rotor blade produces a respective vortex and (ii) the respective vortices cause the rotor unit to produce a sound output having an energy distribution defined, at least in part, by a set of frequencies, wherein the set of frequencies includes a fundamental frequency, one or more harmonic frequencies, and one or more non-harmonic frequencies having a respective strength greater than a threshold strength.

Axial airplane airscrew-, fan-, and wind turbine blade of low loading characterised by the fact that the aspect ratio of the airscrew-, fan- and wind turbine blades is low; near to the wide blade ends, but in an appropriate distance an aperture of appropriate length and widthalmost parallel to the side of the blade endis formed, which connects the surfaces of lower and higher pressure. When being operated, the air flowing through this aperture eliminates the turbulence formed at the end of the blades.

With regards to diameter, the choice of the distribution of strings on the airscrew blade (its blade width) caused problems in case of adapting a huge performance, as well as there was a need to form wide blade ends. The losses resulting from the circular flow of the blade ends were, however, increased dramatically.

In case of adapting wide blade ends, the invention uses the phenomenon known from physics as interference, more precisely whirl interference to reduce or eliminate the loss of potential resulting from the circular flow of the blade ends tips on the airscrew.

A whirl of contrary direction and of equal angular momentum (or impulse momentum) is induced at the ends of the airscrew blades, which by this eliminates or significantly reduces the whirls appearing at the end of wide blades and causing losses.

As a result of this, a tractive force evolves on the airscrews and the range of action of the aircraft as well as the time spent on flying can be increased.

Its application is also recommended on wind turbine rotor blades.

If applied, it reduces the resonant vibrations occurring on the blades and the turbines, and thus extending their lifetime significantly. Using aerodynamic braking the forming of the pivoting tip is more effective and less vibrating. The blade edges are working as slotted flaps.

An aerial vehicle is provided including rotor units connected to the aerial vehicle, and a control system configured to operate at least one of the rotor units. The rotor unit includes rotor blades, wherein each rotor blade includes a surface area, and wherein an asymmetric parameter is defined, at least in part, by the relationship between the surface areas of the rotor blades. The value of the asymmetric parameter is selected such that the operation of the rotor unit: (i) moves the rotor blades such that each rotor blade produces a respective vortex and (ii) the respective vortices cause the rotor unit to produce a sound output having an energy distribution defined, at least in part, by a set of frequencies, wherein the set of frequencies includes a fundamental frequency, one or more harmonic frequencies, and one or more non-harmonic frequencies having a respective strength greater than a threshold strength.

Sounds are generated by an aerial vehicle during operation. For example, the motors and propellers of an aerial vehicle generate sounds during operation. Systems, methods, and apparatus may actively adjust the position and/or configuration of one or more propeller blades of a propulsion mechanism to generate different sounds and/or lifting forces from the propulsion mechanism.

Axial airplane airscrew-, fan-, and wind turbine blade of low loading characterised by the fact that the aspect ratio of the airscrew-, fan- and wind turbine blades is low; near to the wide blade ends, but in an appropriate distance an aperture of appropriate length and widthalmost parallel to the side of the blade endis formed, which connects the surfaces of lower and higher pressure. When being operated, the air flowing through this aperture eliminates the turbulence formed at the end of the blades.

With regards to diameter, the choice of the distribution of strings on the airscrew blade (its blade width) caused problems in case of adapting a huge performance, as well as there was a need to form wide blade ends. The losses resulting from the circular flow of the blade ends were, however, increased dramatically.

In case of adapting wide blade ends, the invention uses the phenomenon known from physics as interference, more precisely whirl interference to reduce or eliminate the loss of potential resulting from the circular flow of the blade ends tips on the airscrew.

A whirl of contrary direction and of equal angular momentum (or impulse momentum) is induced at the ends of the airscrew blades, which by this eliminates or significantly reduces the whirls appearing at the end of wide blades and causing losses.

As a result of this, a tractive force evolves on the airscrews and the range of action of the aircraft as well as the time spent on flying can be increased.

Its application is also recommended on wind turbine rotor blades.

If applied, it reduces the resonant vibrations occurring on the blades and the turbines, and thus extending their lifetime significantly. Using aerodynamic braking the forming of the pivoting tip is more effective and less vibrating. The blade edges are working as slotted flaps.