Rapid digitized storage of seed-particle-track images in microscopically inhomogeneous flows

The light scattered from submicrometer seed particles illuminated by a chopped cw argon laser is imaged on a silicon-intensified-target vidicon. A simple means of rapidly sampling the vidicon output, to store the records of particle-track images on a digital oscilloscope, is described. The digitized records so obtained are suitable for automated processing. Observations of microscale velocity fluctuations, recorded at frame times down to 10 msec, are reported and found to be consistent with earlier results from interferometric laser anemometry. The technique is applicable to turbulent-flow studies over a wide range of velocities and distance scales.