Basics of two-phase flow
Pneumatic conveying of bulk products

In pneumatic handling systems operating in dilute phase, solid particles flow through the piping system suspended in the gas. The entrainment of the particles by the gas is due to a transfer of energy from the gas to the particles. The behavior of these particles suspended in a gas is characterized by the influence of gravitational forces. Their inertia prevents them from following the fluid flow, resulting in a difference in velocity between the gas and the particles, known as the "relative sliding velocity". This is a function of a large number of factors, in particular particle size, density, shape and concentration.