Pneumatic transportation of bulk materials has become a very important technology in industries. It is well established that different flow regimes can rise in such transportation processes depending on operational conditions. This paper presents a numerical study of the transportation of solid particles in a horizontal pipeline by means of discrete particle simulation, where both the motion of discrete particle and the flow of continuum gas are three-dimensional. The results show that three flow regimes, i.e. suspension flow, stratified flow, and slug flow, and the corresponding gas velocity - pressure drop phase diagram can be successfully reproduced and agree well with the experiments in the literature. In addition, an unstable flow pattern observed in experiments is also obtained in the simulation. Different particle-fluid forces including fluid drag force, pressure gradient force, Saffman lift force, and Magnus lift force, are analysed. It shows that the fluid drag force is a dominant force in all the flow regimes, the lift forces can be safely ignored, and the pressure gradient force play a role in slug flow.
Keywords: discrete particle simulation, computational fluid dynamics, gas-solid flow, flow regimes, pneumatic conveying