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 velocity 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 the CCD camera to achieve the frame-straddling illumination mode for the measurement of particle velocities. Silhouetted particle images are acquired with two black-and-white CCD cameras in stereo configuration. The particle images are analysed with a specially devised procedure, which can faithfully detect the perimeters both of spherical and of non-spherical particle images. The use of stereo imaging permits measurement of all three velocity components 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 particle-sizing techniques based on back lighting. The technique developed here is capable of sizing 10-500µm particles to within ±4µm inaccuracy. The validity of the technique is demonstrated by the measurement of a variety of transparent/opaque and spherical/non-spherical particles falling down a vertical pipe.