High speed hand driers, such as the ones made by Dyson, dry hands efficiently by ejecting a jet a a high speed – up to half the speed of sound. The jet comes out of the nozzle as laminar flow, mixes with the surrounding air, becomes turbulent and radiates noise.
The jet contains coherent structures that are efficient for sound radiation
Schlieren image from a thin rectangular jet
We are modelling the noise sources and finding ways to reduce the noise.