High-Speed Non-Intrusive Measurement Techniques for the Visualization of Droplet Clouds

The overall objective of the proposed work is to devise a high-speed non-intrusive technique to visualize droplets in laboratory/test site environments in static and dynamic modes. The primary objective of Phase I was to develop a laboratory-scale prototype system of digital/analog 3-D static as well as dynamic single droplet holography. An additional objective was to develop algorithms to visualize and determine the size, shape, and velocity of a droplet in a lab setup. The method should be extendable from a single droplet to multiple droplets such as in a cloud or rain, and to other kinds of objects such as sand particles. We have developed the lab setup and methodology of droplet 3-D shape/size visualization and deformation using digital holography, and analog dynamic holography using photorefractive materials and holocameras. After careful comparison of both approaches including experimental results and inferences, convenience, speed, and cost, we suggest that digital holographic scheme(s) should be the preferred method of choice in Phase II for multiple droplets, sand particles, etc., and in high-speed dynamic laboratory/test site environments. The digital holographic scheme will be supported/augmented using inferences from analog dynamic holography as required, e.g., during multiple droplet characterization in a cloud/rain.