Oscillating air jets for helicopter rotor aerodynamic control and BVI noise reduction

A method of changing an amount of lift generated by a rotor blade, the rotor blade having an aerodynamic surface and an interior volume, the aerodynamic surface including an upper surface and a lower surface, the method comprising the following steps:

• providing at least one aperture on the lower surface of the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable between a first position and a second position, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• receiving into a controller an instruction to increase an amount of lift generated by the rotor blade;
• and
• moving the diaphragm between the first position and the second position to thereby increase the amount of lift generated by the rotor blade.

A method of changing an amount of lift generated by a rotor blade, the rotor blade having an aerodynamic surface and an interior volume, the aerodynamic surface including an upper surface and a lower surface, the method comprising the following steps:

• providing at least one aperture on the lower surface of the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable between a first position and a second position, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• receiving into a controller an instruction to generate a negative pitching moment on the rotor blade;
• and
• moving the diaphragm between the first position and the second position to thereby increase the amount of lift generated by the rotor blade.

A method of changing an amount of lift generated by a rotor blade, the rotor blade having an aerodynamic surface and an interior volume, the aerodynamic surface including an upper surface and a lower surface, the method comprising the following steps:

• providing at least one aperture on the aerodynamic surface of the rotor blade, the step of providing at least one aperture comprising a step of providing at least one aperture on the upper surface of the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable between a first position and a second position, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• and
• receiving into a controller an instruction to decrease an amount of lift generated by the rotor blade;
• moving the diaphragm between the first position and the second position to thereby change the amount of lift generated by the rotor blade, the step of moving the diaphragm comprising a step of moving the diaphragm between the first position and the second position to thereby decrease an amount of lift generated by the rotor blade.

A method of changing an amount of lift generated by a rotor blade, the rotor blade having an aerodynamic surface and an interior volume, the aerodynamic surface including an upper surface and a lower surface, the method comprising the following steps:

• providing at least one aperture on the aerodynamic surface of the rotor blade, the step of providing at least one aperture comprising a step of providing at least one aperture on the upper surface of the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable between a first position and a second position, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• receiving into a controller an instruction to generate a positive pitching moment on the rotor blade;
• and
• moving the diaphragm between the first position and the second position to thereby change the amount of lift generated by the rotor blade, the step of moving the diaphragm comprising a step of moving the diaphragm between the first position and the second position to thereby decrease an amount of lift generated by the rotor blade.

A method of changing an amount of lift generated by a rotor blade, the rotor blade having an aerodynamic surface and an interior volume, the aerodynamic surface including an upper surface and a lower surface, the method comprising the following steps:

• providing at least one aperture on the aerodynamic surface of the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable between a first position and a second position, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• moving the diaphragm between the first position and the second position to thereby change the amount of lift generated by the rotor blade, the step of moving the diaphragm comprising a step of moving the diaphragm between the first position and the second position at a predetermined frequency to thereby affect an amount of lift generated by the rotor blade;
• and
• changing the predetermined frequency, to thereby change an amount of lift generated by the rotor blade.

A method of changing an amount of lift generated by a rotor blade, the rotor blade comprising an upper surface, a lower surface, and an interior volume, the method comprising the following steps:

• providing at least one aperture on the rotor blade;
• providing a diaphragm in the interior volume of the rotor blade, the diaphragm being movable in a first direction and a second direction, whereby movement of the diaphragm in the second direction pushes air out of the at least one aperture and movement of the diaphragm in the first direction draws air into the at least one aperture;
• moving the diaphragm in both the first direction and the second direction at a predetermined energization level, the predetermined energization level corresponding to a predetermined range of motion of the diaphragm in the first and second directions, and corresponding to a speed of movement of the diaphragm in the first and second directions, whereby movement of the diaphragm at the predetermined energization level results in air being pushed out of and drawn into the at least one aperture at a peak velocity, and whereby movement of the diaphragm at the predetermined energization level affects the amount of lift generated by the rotor blade;
• and
• changing the predetermined energization level, to thereby change at least one of the range of motion and the speed of movement of the diaphragm, the changing of the predetermined energization level changing an amount of lift generated by the rotor blade.

A method of reducing blade-vortex-interaction (BVI) noise generated by a rotor blade, the rotor blade including an interior, a tip end, a root end, a leading edge, a trailing edge, an upper surface, and a lower surface, the method comprising the following steps:

• providing a sensor assembly in close proximity to the rotor blade;
• providing on the rotor blade a device for changing a lift generated by the rotor blade, the device when activated being adapted to change the lift of the rotor blade while the rotor blade is maintained at a constant rotational velocity, wherein the step of providing on the rotor blade a device for changing a lift generated by the rotor blade comprises the steps of providing at least one aperture on the rotor blade and providing a diaphragm in the interior of the rotor blade, the diaphragm being adapted to be activated and moved between a first position and a second position at a frequency, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• determining with the sensor assembly a change in pressure on the rotor blade near the leading edge of the rotor blade, the change in pressure having a magnitude;
• and
• activating the device to change the lift of the rotor blade in order introduce a compensating pressure onto the rotor blade, the compensating pressure being adapted to attenuate the magnitude of the change in pressure.

A method of reducing blade-vortex-interaction (BVI) noise generated by a rotor blade, the rotor blade including an interior, a tip end, a root end, a leading edge, a trailing edge, an upper surface, and a lower surface, the method comprising the following steps:

• providing a sensor assembly in close proximity to the rotor blade;
• providing on the rotor blade a device for changing a lift generated by the rotor blade, wherein the step of providing on the rotor blade a device for changing a lift generated by the rotor blade comprises the steps of providing at least one aperture on the rotor blade and providing a diaphragm in the interior of the rotor blade, the diaphragm being adapted to be activated and moved between a first position and a second position at a frequency, whereby movement of the diaphragm from the first position to the second position pushes air out of the at least one aperture and movement of the diaphragm from the second position to the first position draws air into the at least one aperture;
• first determining with the sensor assembly that a decrease in pressure has occurred on the lower surface of the rotor blade near the leading edge of the rotor blade;
• first activating the device to increase a lift of the rotor blade;
• second determining with the sensor assembly that an increase in pressure has occurred on the lower surface of the rotor blade near the leading edge of the rotor blade;
• and
• second activating the device to decrease a lift of the rotor blade.