Lufthansa has taken delivery of the first Airbus A320 fitted with noise-reducing vortex generators (VGs). All its new A320-family aircraft will have the mod, and all the 157 aircraft already in service will be retrofitted, for a total on more than 200 quieter Airbuses - but you will have to look closely to see the modification:
An anticlimax, huh? Usually, aerodynamicists use lots of vortex generators to fix flow problems - whole fields of them sometimes, like the wing of this Gloster Javelin:
Photo: Adrian Pingstone, via Wikipedia
The VGs on the A320 have a very specific purpose. They reduce noise on final approach by up to 2dB by eliminating two annoying tones caused by air flowing over circular fuel-tank pressure equalization vents under the wing - like blowing across the mouth of a bottle, Lufthansa says. The VG creates a vortex in front of the vent and prevent the noise. Quite clever, actually.
Development of the vortex generators by Airbus for the A320 family was the result of research carried out by Lufthansa and German Aerospace Center DLR, the airline says, flyover measurements showing the VGs could eliminate the unpleasant tones and reduce the total noise on approach.