QUANTITATIVE MEASUREMENTS OF INTERNAL CIRCULATION IN DROPLETS USING FLOW TAGGING VELOCIMETRY

We demonstrate the use of the photoactivated nonintrusive tracking of molecular motion flow tagging technique to obtain quantitative velocit y measurements in free falling water droplets and in electrohydrodynam ic Taylor cones. A simple ray tracing procedure is outlined to remove the optical distortion caused by the droplet surface curvature. This c orrection is applied to free falling droplet images, and the vertical component of velocity is measured across the droplet. Maximum vertical velocities in the droplet are 15.9 +/- 3.3 mm/s. Without ray tracing, the optical distortion is shown to cause errors in the sign of veloci ty as well as errors of over 100% in velocity magnitude. Preliminary v elocity measurements in a Taylor cone are also presented. Centerline v elocities in the Taylor cone are approximately 4 mu/s.