Stereo imaging for simultaneous measurement of size and velocity of particles in dispersed two-phase flow

A stereo-imaging technique for the simultaneous measurement of size and vel ocity of solid/liquid particles in dispersed two-phase flows is developed. Particles are illuminated with back light provided by the two strobe lamps. Double-pulsed strobe flashing is done synchronously with the framing of th e CCD camera to achieve the frame-straddling illumination mode for the meas urement of particle velocities. Silhouetted particle images are acquired wi th two black-and-white CCD cameras in stereo configuration. The particle im ages are analysed with a specially devised procedure, which can faithfully detect the perimeters both of spherical and of non-spherical particle image s. The use of stereo imaging permits measurement of all three velocity comp onents and also resolution of the depth-of-field effect in particle sizing, the problem that has been a key subject in the development of accurate par ticle-sizing techniques based on back lighting. The technique developed her e is capable of sizing 10-500 mu m particles to within +/-4 mu m inaccuracy . The validity of the technique is demonstrated by the measurement of a var iety of transparent/opaque and spherical/non-spherical particles falling do wn a vertical pipe.