Effects of gas flow on granular size separation.

A gas flow is introduced into a vibrating bed from its perforated bottom to clarify the effects of gas flow on granular size separation. The rising or sinking time of a single intruder does not follow a monotonic relationship, and the granular mixtures show four different types of distribution with increasing gas velocity. The different drag forces exerted on large particles and small ones are the main factors that influence the granular size separation. Under the "wall effect" the gas flow may speed up the rising of the large particle, and cause a change in size distribution.