Solid particle velocity in vertical gaseous suspension flows

An optical method. which is based on cross-correlating the signals of two photo-sensors. is applied to measure the average velocity of solid particles transported vertically by a turbulent air stream. Particle velocities measured by the method showed two interesting features; the relative velocity was smaller than the terminal velocity of a single particle at lower air velocities but greater at higher velocities. and for smaller sizes of particles it tended to depend on the solid concentration as well. An empirical correlation was presented for the average particles velocity and tested with literature data. The average drag coefficients. which were evaluated indirectly from the measured relative velocities and the pressure drop due to solids alone. exhibited significant increase compared with the standard ones.