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 of the fluid flow on the surface. In various embodiments, the transverse momentum injection actuators may be operated at frequencies less than 10,000 Hertz.

A ducted fan assembly includes a duct having an inlet, an inner surface, an expanding diffuser and an outlet. A fan disposed within the duct between the inlet and the expanding diffuser is configured to rotate about a fan axis to generate airflow. An active flow control system includes a plurality of injection zones circumferentially distributed about the inner surface. The expanding diffuser has a diffuser angle configured to create flow separation when the airflow is uninfluenced by the active flow control system such that the airflow has a thrust vector with a first direction that is substantially parallel to the fan axis. Injection of pressurized air from one of the injection zones asymmetrically reduces the flow separation between the airflow and the expanding diffuser downstream of that injection zone such that the thrust vector of the airflow has a second direction that is not parallel to the first direction.

An aircraft having reverse thrust capabilities includes a fuselage, a plurality of flight components, a pilot control located within the fuselage, a sensor attached to the pilot control configured to detect an aircraft datum from the pilot control, and a flight controller, located within the fuselage, the flight controller configured to receive the aircraft datum from the sensor, and initiate a reverse torque command of a flight component of the plurality of flight components as a function of the aircraft datum.

An aircraft having reverse thrust capabilities includes a fuselage, a plurality of flight components, a pilot control located within the fuselage, a sensor attached to the pilot control configured to detect an aircraft datum from the pilot control, and a flight controller, located within the fuselage, the flight controller configured to receive the aircraft datum from the sensor, and initiate a reverse torque command of a flight component of the plurality of flight components as a function of the aircraft datum.

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.

In order to suppress aeroelastic instabilities on a transonically operating aircraft comprising a pair of wing halves at which a transonic flow forms spatially limited supersonic flow regions that each, in a main flow direction of the flow, end in a compression shock, a boundary layer of the flow is temporarily thickened-up in at least one supersonic flow region at at least one of the two wing halves, when approaching a flight envelope of the aircraft with increasing flight Mach number of the aircraft. The boundary layer of the flow is thickened-up to such an extent that the compression shock at the end of the respective supersonic flow region at the present flight Mach number of the aircraft induces a separation of the boundary layer of the flow from the wing half.

In order to suppress aeroelastic instabilities on a transonically operating aircraft comprising a pair of wing halves at which a transonic flow forms spatially limited supersonic flow regions that each, in a main flow direction of the flow, end in a compression shock, a boundary layer of the flow is temporarily thickened-up in at least one supersonic flow region at at least one of the two wing halves, when approaching a flight envelope of the aircraft with increasing flight Mach number of the aircraft. The boundary layer of the flow is thickened-up to such an extent that the compression shock at the end of the respective supersonic flow region at the present flight Mach number of the aircraft induces a separation of the boundary layer of the flow from the wing half.

The present disclosure presents systems, apparatuses, and methods of active flow controls for dissipating tip vortices. In this regard, a method comprises positioning one or more fan-shaped plasma actuators on an end surface of a tip of one or more airfoils of an aircraft, wherein the fan-shaped plasma actuators are surface compliant with the surface of the tip of the one or more airfoils; and activating the one or more fan-shaped plasma actuators during a flight of the aircraft, wherein at least one tip vortex generated by a flight of the aircraft is reduced by an introduction of one or more vortices generated by the one or more fan-shaped plasma actuators on the end surface of the tip of the one or more airfoils of the aircraft. Other systems, apparatuses, and methods are also presented.

The present disclosure presents systems, apparatuses, and methods of active flow controls for dissipating tip vortices. In this regard, a method comprises positioning one or more fan-shaped plasma actuators on an end surface of a tip of one or more airfoils of an aircraft, wherein the fan-shaped plasma actuators are surface compliant with the surface of the tip of the one or more airfoils; and activating the one or more fan-shaped plasma actuators during a flight of the aircraft, wherein at least one tip vortex generated by a flight of the aircraft is reduced by an introduction of one or more vortices generated by the one or more fan-shaped plasma actuators on the end surface of the tip of the one or more airfoils of the aircraft. Other systems, apparatuses, and methods are also presented.

Systems and method for active control of stationary vortices for aerodynamic structures are disclosed herein. In one embodiment, a method for active control of vortices over a solid surface includes: generating vortices proximate to the solid surface; sensing locations of vortices by printed skin sensors; and maintaining the vortices in their fixed spanwise positions with respect to the solid surface by actuation of printed skin actuators.