Development of a laser displacement probe to measure particle impact velocities in vibrationally fluidized granular flows

A new laser displacement probe was developed to measure the impact velocities of particles within vibrationally fluidized beds. Key features of the displacement signals were interpreted using an analysis of the motion of a vibrating particle contacting the vibrating sensor window. The sensor output was also used to measure bulk flow velocity along the probe window and to provide a measure of the media packing. The probe was demonstrated in a tub vibratory finisher containing either steel or porcelain spheres. Sample measurements were made at several fixed locations in the vibratory tub, in three orthogonal directions. The displacement signals from the laser sensors were analyzed to obtain the probability distribution functions of the impact velocity of the particles. The impact velocity was affected by the orientation of the laser probe relative to the bulk flow velocity, and the density and elastic properties of the granular media. The average impact velocity of the porcelain balls was greater than that of the steel balls. The impact velocities of the particles were largely independent of their bulk flow speed and packing density. The present laser sensor impact velocity measurements are compared with those obtained in a previous study using an impact force sensor.