Aerodynamic effect on charged droplet train ejected from a 26 μm nozzle

The fundamental characteristics of motion of a droplet ejected from a nozzle with 26 μm aperture have been carefully investigated. Droplets ejected are periodically charged and deflected by the deflection field. The behavior of charged and uncharged droplets in air is examined by a CCD camera, and from its images velocities and deflection distances are calculated. The results indicate that droplet train is decelerated linearly by the aerodynamic resistance, which is much smaller than the Stokes resistance for a single particle. It was found that there are two types of coalescence: one is due to Coulomb force between a charged and an uncharged droplet and the other is due to purely aerodynamic effect which is caused by the vacancy of the train. Deflected charge droplets showed complicated motion because of Coulomb and aerodynamic effects when they are proceeding in air. A factor to the Stokes resistance is shown to be between 0.5 and 0.6. Thus, the aerodynamic resistance for the train of droplets is much smaller than for the single particle.