Miniature vortex generators could help to reduce low-speed aerodynamic noise

Airbus is studying the use of miniature vortex generators on wing high-lift devices to alleviate aerodynamic noise at low speeds.

The idea, recently patented in the USA, involves comb- or brush-like devices that protrude into the airflow at the chordwise edges of leading and trailing-edge high-lift devices to break the main vortex into many smaller vortices, producing significantly less aerodynamic noise.

The Airbus Deutschland team behind the invention notes that previous flow-stabilisation techniques such as winglets or wingtip fences, while having a positive effect on drag, offer minimal noise reduction. Wingtip devices reduce the strength of wingtip vortices, but much of an aircraft's low-speed noise emanates from vortices generated at discontinuities along the leading and trailing edges.

The Hamburg group's vortex generator would consist of a rigid comb-like structure, or a flexible brush-like structure, protruding from the high-lift device's inboard or outboard profile edge, or trailing edge. They would need to be installed over one-fifth to two-thirds of the chord length of the device. The relatively small protrusions generate a greater number of small vortices, which break up and take energy away from the main vortex, without significantly affecting the wing's aerodynamics. The noise produced by these small vortices is greatly reduced when compared to the single, large vortex.

The team says the design is simple, cheap and lightweight, and it would be adaptable to different wing geometries and flight conditions. More importantly, the devices have hardly any negative effects on the aircraft's overall capacity and operation, the aerodynamic effect of the control surfaces and particularly the lift effect of the slats and flaps.

Source: Flight International