Velocity and porosity relationships within dense phase pneumatic conveying as studied using coupled CFD-DEM

This study used a 3D coupled CFD-DEM model to study velocity and porosity relationships within horizontal dense phase pneumatic conveying. Inlet velocities, initial layer fractions and initial slug lengths were varied for a total of 72 single slug simulations. The linear relationship between particle velocity and slug velocity was examined and the origins and contributions of individual variables were looked at in detail. It was found that the slug velocity to particle velocity relationship can be defined using slug to bulk density ratio and propagation velocity. It was also found that within a single slug system, slugs tend to their 'preferred' steady-state length which is a function of inlet velocity and stationary layer ahead of the slug. Another finding is that hydraulic jump can be used as an analogy to the interaction between slug front and the stationary layer. This analogy can be used to define a boundary for slug flow as well as help predict slug porosity.