FLOW VELOCITY-MEASUREMENTS USING DIGITAL PULSED LASER VELOCIMETRY

Digital pulsed laser velocimetry (DPLV) is a novel full-field, two-dimensional, noninvasive, quantitative flow visualization technique. A description of the technique, which uses direct digitization of single- or two-phase flow images using a high-resolution imaging system and a high-power pulsed laser, is presented. Images (ten consecutive frames of data separated by a time increment of 150 ms) of single- and two-phase flow over a step are acquired with a high-resolution camera. Each of these ten frames contains the images of tracer articles or bubbles at that one instant of time. The image data was stored for further analysis by new image processing and analysis software developed specifically for flow experiments. An image finding, smoothing, and defining program was developed. This program groups appropriate pixels into particles, smoothes the image, and calculates important parameters for the image. Another program was developed to match the particles from each of the frames into tracks through time. The program uses a statistical technique to determine the best possible path of the particles. The most important capability of pulsed laser velocimetry is the ability to use these image processing techniques to capture simultaneous and quantitative rather than qualitative information.