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High-resolution cross-correlation PIV on photographic film

An adaptation of current image shifting techniques has been developed that permits cross-correlation PIV analysis of non- overlapping images recorded on photographic media. The image acquisition technique utilizes pulsed lasers to produce two singly exposed sub-images of particles in one photographic frame. The technique can also provide images suitable for cross-correlation analysis on digitally recorded images without the need for a specialized camera. An adaptive cross- correlation PIV analysis method is employed to extract the in- plane velocity field information with high velocity sampling resolution and large velocity dynamic range. Further capabilities and limitations of the technique are presented as well as an analysis of the associated measurement errors. Some of the more interesting problems that were encountered during the development of the experimental technique are also discussed. The application of this method to the unsteady flow of a vortex ring will be illustrated as an example. High spatial resolution measurements using film recording have yielded the detailed instantaneous 2-D velocity and vorticity fields. Measurements made from digital recordings using this technique provide the evolution of instantaneous in-plane velocity and vorticity fields.