VISUALIZATION OF AERODYNAMICALLY FOCUSED SUBSONIC AEROSOL JETS

The phenomenon of aerosol focusing in jets is illustrated by photographing the light scattered from 3 mum polystyrene spheres suspended in air accelerating at near atmospheric pressure through a thin plate orifice nozzle. The effect of varying particle inertia (Stokes number S) and percentage of sheath air surrounding the aerosol is studied for moderately compressible jets at Mach numbers ranging from 0.7 to 0.04. Jet Reynolds numbers ranged from 250 to 7500, corresponding to nearly inviscid flows for a thin plate orifice. Enrichments of the aerosol number density by factors of 300 or more are demonstrated in jets driven by a pressure difference of only 50 torr. Aerosol beam focal point widths as narrow as 1% of the nozzle diameter are observed.