Making wings sing

Using sound to control the flow of air over an aircraft's wing, greatly boosting its lift, has propelled UNSW aerospace engineering student Ian Salmon into the list of finalists for the Australian 2005 Fresh Science awards.

Salmon, who works at Qantas as an aircraft development engineer, is working on applying this idea to a new generation of light aircraft. He has developed a technique in which an aircraft's wing is covered with flexible plastic panels which vibrate when an electric current is passed through them, producing sound.

At a carefully selected frequency, the air passing over the wing can be made to remain more closely attached, increasing the wing's efficiency.

While the theory behind the technique is not new, the method of applying sound directly to the wing during flight is novel. Previous studies used large speakers pointing at a model in a wind tunnel with encouraging results but painful sound levels.

"This new method grew from the desire to carry a lightweight sound source on the aircraft, and to apply sound exactly where it was needed, rather than spraying it everywhere," Salmon said. "Obviously one thing we did not want to do was to make aircraft noisier."

It's unlikely that his method will be used on large commercial jets. "The beneficial effects are far more pronounced for small, slow aircraft which fly in conditions where the air's viscosity, or 'stickiness' has more influence on the air's behaviour."

Although the kind of sound which is most effective in manipulating airflow is a single-frequency tone, other forms, including music, have shown some effect.

Salmon is one of 13 Fresh Science finalists. His research was undertaken at UNSW as part of a BE thesis under the supervision of Associate Professor NA Ahmed.

For more information on the 2005 Fresh Science awards, visit the Fresh Science website.