PARTICLE IMPACTION PATTERNS FROM A CIRCULAR JET

The surface distributions of particles that have impacted from a circular jet have been measured by optical microscopy and image analysis. Monodisperse, 3-mum ammonium fluorescein particles were impacted onto greased surfaces at various velocities from the nozzle. The spot radius is approximately equal to the nozzle radius at square-root St = 0.8. At square-root St = 1.6, the spot radius is about half of the nozzle radius; convergence of the flow into the nozzle results in a focusing effect. The surface density has a peak which moves out to larger radius with decreasing Stokes number, reaching the nozzle radius at about square-root St = 0.5. The radii enclosing 10.5% and 70.3% of the particles as a function of square-root St are in good agreement with the theoretical predictions of Marple (1970); however, the upturn of the experimental data for square-root St < 0.5 is somewhat sharper. Empirical formulas were fitted to the data.