A raised structure for reducing frictional drag due to viscosity of a flow toward an object in a direction forming an acute angle with an end portion of the object. The raised structure includes a plurality of raised bodies provided on a surface of the leading edge of the object at a downstream side of a stagnation point of the main flow, wherein a height of each raised body changes along a smooth convex curve, and the raised bodies are arranged in an array to form a first uneven shape changing periodically in a first cross section having a constant distance from the stagnation point and orthogonal to the surface, and a second uneven shape changing in a second cross section that is orthogonal to a line composed of the stagnation point and the first cross section, the second uneven shape having concave portions and convex portions that change periodically.

A turbomachine includes a rotor and a stator, the stator having a plurality of profiled structures, each profiled structure being elongated in a direction of elongation in which the profiled structure has a length exposed to an airflow, and having a leading edge and/or a trailing edge, at least one of which is profiled and has, in said direction of elongation, serrations defined by a succession of peaks and troughs and having a geometric pattern transformed, over at least a part of said length exposed to the airflow, by successive scaling, via multiplicative factors, in the direction of elongation and/or transverse to the direction of elongation. The geometric pattern, as defined with reference to a radial distribution of the integral scale of the turbulence, evolves in a non-periodic manner.

A ducted fan assembly for generating thrust during edgewise forward flight. The ducted fan assembly includes a duct having an inlet with a leading portion and a diffuser with a trailing portion during the edgewise forward flight. A fan disposed within the duct is configured to rotate relative to the duct about a fan axis to generate an airflow through the duct from the inlet to the diffuser. An active flow control system includes a plurality of injectors including a first injector configured to inject pressurized air substantially tangential with the leading portion of the inlet and a second injector configured to inject pressurized air substantially tangential with the trailing portion of the diffuser such that when the injectors are injecting pressurized air, flow separation of the airflow at the leading portion of the inlet and the trailing portion of the diffuser is reduced.

A fluid diverting air inlet includes an intake opening through an outer surface of an enclosure for receiving air flowing outside the outer surface. The intake opening ramps downwardly below the outer surface to define an intake passageway. An air diversion device is formed by lateral sidewalls of the intake opening that extend vertically above the outer surface. The lateral sidewalls converge together at an upstream end of the air inlet, and the lateral sidewalls diverge apart towards a downstream end of the air inlet. Flanges extend outwardly from the tops of the lateral sidewalls such that divided air passageways for boundary layer fluids are formed on each side of the air diversion device. The sidewalls and flanges are integrated with the air inlet such that fluid moving immediately adjacent the outer surface of the enclosure is diverted around the air inlet to avoid ingestion into the intake opening.

A fluid diverting air inlet includes an intake opening through an outer surface of an enclosure for receiving air flowing outside the outer surface. The intake opening ramps downwardly below the outer surface to define an intake passageway. An air diversion device is formed by lateral sidewalls of the intake opening that extend vertically above the outer surface. The lateral sidewalls converge together at an upstream end of the air inlet, and the lateral sidewalls diverge apart towards a downstream end of the air inlet. Flanges extend outwardly from the tops of the lateral sidewalls such that divided air passageways for boundary layer fluids are formed on each side of the air diversion device. The sidewalls and flanges are integrated with the air inlet such that fluid moving immediately adjacent the outer surface of the enclosure is diverted around the air inlet to avoid ingestion into the intake opening.

Systems and methods are described herein to implement transverse momentum injection at low frequencies to directly modify large-scale eddies in a turbulent boundary layer on a surface of an object. A set of transverse momentum injection actuators may be positioned on the surface of the object to affect large-scale eddies in the turbulent boundary layer. The system may include a controller to selectively actuate the transverse momentum injection actuators with an actuation pattern to affect the large-scale eddies to modify the drag, fluid mixing, heat transfer, and/or other interactions of the fluid flow with the surface. In various embodiments, the transverse momentum injection actuators may be operated at frequencies less than 10,000 Hertz.

A method for controlling a flying projectile which rotates during flight, comprising: determining an angle of rotation of an inertial mass spinning about an axis during flight; and controlling at least one actuator for altering at least a portion of an aerodynamic structure, selectively in dependence on the determined angle of rotation and a control input, to control aerodynamic forces during flight. An aerodynamic surface may rotate and interact with surrounding air during flight, to produce aerodynamic forces. A sensor determines an angular rotation of the spin during flight. A control system, responsive to the sensor, produces a control signal in dependence on the determined angular rotation. An actuator selectively alters an aerodynamic characteristic of the aerodynamic surface in response to the control signal.

A method for controlling a flying projectile which rotates during flight, comprising: determining an angle of rotation of an inertial mass spinning about an axis during flight; and controlling at least one actuator for altering at least a portion of an aerodynamic structure, selectively in dependence on the determined angle of rotation and a control input, to control aerodynamic forces during flight. An aerodynamic surface may rotate and interact with surrounding air during flight, to produce aerodynamic forces. A sensor determines an angular rotation of the spin during flight. A control system, responsive to the sensor, produces a control signal in dependence on the determined angular rotation. An actuator selectively alters an aerodynamic characteristic of the aerodynamic surface in response to the control signal.

A flow control apparatus includes a plasma actuator, a storage device, and a control circuit. The plasma actuator causes discharge in a discharge area by applying an alternating-current (AC) voltage between electrodes to form an induced flow of gas. The electrodes are shifted relatively to each other with a dielectric disposed between them. The storage device stores a changing condition of an AC voltage waveform for changing a gas flow state formed in a flow control area of gas from a first state to a second state by adding the induced flow of gas. The control circuit refers to the changing condition of the AC voltage waveform and control the AC voltage waveform based on the changing condition of the AC voltage waveform, in a case of changing the gas flow state formed in the gas flow control area from the first flow state to the second flow state.

A flow control apparatus includes a plasma actuator, a storage device, and a control circuit. The plasma actuator causes discharge in a discharge area by applying an alternating-current (AC) voltage between electrodes to form an induced flow of gas. The electrodes are shifted relatively to each other with a dielectric disposed between them. The storage device stores a changing condition of an AC voltage waveform for changing a gas flow state formed in a flow control area of gas from a first state to a second state by adding the induced flow of gas. The control circuit refers to the changing condition of the AC voltage waveform and control the AC voltage waveform based on the changing condition of the AC voltage waveform, in a case of changing the gas flow state formed in the gas flow control area from the first flow state to the second flow state.