<title>Full-field velocity imaging technique using high-energy pulsed laser velocimetry</title>

Abstract

Digital Pulsed Laser Velocimetry (DPLV) is a novel full-field, two dimensional, noninvasive, quantitative flow visualization technique. The technique described here includes the use of direct digitization of the images for flow analysis using a high resolution imaging system. The image data is stored for further analysis by a series of new image processing and analysis software developed for flow experiments. The imaging processing and analysis software developed includes a compression program for reducing storage requirements of the image data to 10%. An image finding, smoothing, and defining program has also been developed. Analysis time has been greatly reduced and the software is now running on a PC/AT compatible. This program groups pixels that could logically be defined as one image, smooths that image and calculates important parameters for the image. In the technique images via a high resolution camera (1024 x 1024), ten consecutive frames of data, separated by a time increment of 150 ms, are recorded. Each of these ten frames contains the images of particles at that one instant of time. A third computer program is developed to match the image from each of the frames into tracks of the particles through time. The program uses a statistical technique to determine the best possible path of the fluid seeds. The ability of pulsed laser velocimetry with these image processing techniques to capture simultaneous and quantitative rather than qualitative information is its most important capability.