According to the present disclosure there is provided an arrangement for influencing liquid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface to induce vortices in the liquid flow. The arrangement further comprises a second section, wherein the first section and second section are movable relative to one another to provide the vortex generator surface.

According to the present disclosure there is provided an arrangement for influencing liquid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface to induce vortices in the liquid flow. The arrangement further comprises a second section, wherein the first section and second section are movable relative to one another to provide the vortex generator surface.

A free-streamline airfoil includes a lower surface which is flat or contoured, and an upper surface that is curved or made of discrete flat elements approximating a curved surface, the upper surface presenting a cavity, a cavity width in an airfoil chordwise direction shorter than the airfoil chord, a position and depth of the cavity triggering a turbulent flow over the airfoil's suction side while preserving the airfoil physical integrity.

A free-streamline airfoil includes a lower surface which is flat or contoured, and an upper surface that is curved or made of discrete flat elements approximating a curved surface, the upper surface presenting a cavity, a cavity width in an airfoil chordwise direction shorter than the airfoil chord, a position and depth of the cavity triggering a turbulent flow over the airfoil's suction side while preserving the airfoil physical integrity.

A wing tip device having a first wing tip device element for attaching at a first wing tip device element root to a tip of an aircraft wing, and a second wing tip device element extending from a second wing tip device element root to a second wing tip device element tip, the second wing tip device element root outboard, when viewed in the wing planform direction, of the first wing tip device element root; the first wing tip device element having a first wing tip device element leading edge and a first wing tip device element trailing edge, and the second wing tip device element having a second wing tip device element leading edge and a second wing tip device element trailing edge; and a fairing between the first and second wing tip device element which extends aft from the second wing tip device element trailing edge.

An aircraft with wing tip devices, for example, folding wing tips, is disclosed. The folding wing tip may have a flight configuration for use during flight, and a ground configuration for use in ground-based operations. The ground configuration creates a shorter wing span than when the aircraft is in the flight configuration. A hinge arrangement protrudes beyond an outer surface of the fixed wing and wing tip device. In order to reduce the aerodynamic effect of the protruding hinge a fairing may be provided. In the flight configuration the fairing comprises a rear portion with a concave surface, such that the fairing acts as a lift-generating surface when the aircraft is in flight.

According to the present disclosure there is provided an arrangement for influencing fluid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface, the vortex generator surface comprising a series of laterally aligned projections, to induce vortices in the liquid flow.

According to the present disclosure there is provided an arrangement for influencing fluid flow, the arrangement comprising: a first section selectively configurable to provide a vortex generator surface, the vortex generator surface comprising a series of laterally aligned projections, to induce vortices in the liquid flow.

A propeller system combines innovative strategies to create a new methodology to reduce propeller or rotor noise. The propeller is specifically aimed for ultra-quiet electrically powered aircraft for use in high proximity aviation, but its low-noise advantages will extend to other purposes. The propeller blade includes geometries, along with size and operational limitations that minimize rotational and vortex noise, vibration and span-wise air flow on the blade. To further reduce noise, the propeller provides greater relative thrust on the inboard portions of the blade than do conventional propellers and provides less than conventional relative thrust including negative thrust at the outermost portions of the blade. The propeller blade includes stepped changes in local blade stiffness at calculated intervals that can reduce resonant blade vibrations and their resultant noise. This ultra-quiet propeller design can also be used for quieting hovercraft, drones, surveillance aircraft, indoor fans, wind tunnels and other applications.

A system for controlling turbulence of fluid flowing past a window includes an imaging device compartment defining an interior and an exterior separated by a window, wherein the window encloses at least a portion of the interior, wherein the exterior includes at least one turbulator on a side upstream of the window positioned to induce turbulence over the entirety of a boundary layer of the fluid flowing past the window for even heat transfer between the fluid and the window.