Abstract

The analysis of velocity fields in fluid flows has greatly profited from the recently introduced technique of double-exposure particle image velocimetry. In this method, the flow is seeded with small light-scattering particles, and the region of interest is illuminated by a thin sheet of light normal to the viewing direction. With a double-pulsed laser source, the twin pairs of particle images recorded photographically yield 2-D velocity information. Interrogation of such records may be done according to speckle photography: a narrow laser beam scans the record, and the particle separation is obtained from the resulting Young’s fringes. Such a pointwise interrogation of a large-field record is quite time-consuming, even when sophisticated electronic image processing equipment is employed.

© 1987 Optical Society of America