Abstract
Based on the multiflash photographs of particle motion, Soo has found that the turbulent intensity of particle motion in solid—gas suspension flow is greater than the corresponding fluid intensity by a factor of as much as three. This has been a source of puzzlement, since it is contrary to what is expected from the nature of particle—fluid interaction. The present paper shows that the ``particle intensity'' as reported by Soo is associated with the velocity distribution of the particles, each of which travels almost uniformly in a straight line at different inclination to the direction of mean flow. This particle behavior is due to collisions between the particles and the wall of the flow channel. Soo's evaluation of the ``particle intensity'' from the same photographic records but using a different optical autocorrelation technique is also examined and found to be in error.