(83b) Saltation length and velocity of granules in air flow

Determination of saltation velocity is one of the key design parameters in pneumatic conveying systems. The aim of this work is to study the mechanism of saltation. Experimental results of measurements of saltation velocity in wind tunnel with very dilute flow are presented. Experiments were carried out with various spherical and non-spherical particles. At each velocity the distribution of halted particles along the tunnel bottom was measured. From this length distribution the median length was found for further analysis. It was found that the median saltation length approaches infinity at a certain threshold velocity. By testing many materials the saltation length over the pipe diameter was found to be a function of Re and Ar numbers. Moreover, the border saltation velocity was found to follow a simple correlation of Re as a function of Ar number. The Re number is modified by a function of the pipe diameter and Ar number is modified by functions of the particle sphericity, coefficient of restitution and coefficient of friction.