Numerical methods in laminar and turbulent flow

Two-fluid approach for plug flow simulations in horizontal pneumatic conveying

Pneumatic conveying is an important technology for industries to transport bulk materials from one location to another. Different flow regimes have been observed in such transportation processes, but the underlying fundamentals are not clear. This article presents a three-dimensional (3-D) numerical study of horizontal pneumatic conveying by a combined approach of discrete element model for particles and computational fluid dynamics for gas. This particle scale, micromechanic approach is verified by comparing the calculated and measured results in terms of particle flow pattern and gas pressure drop. It is shown that flow regimes usually encountered in horizontal pneumatic conveying, including slug flow, stratified flow, dispersed flow and transition flow between slug flow and stratified flow, and the corresponding phase diagram can be reproduced. The forces governing the behavior of particles, such as the particle–particle, particle-fluid and particle-wall forces, are then analyzed in detail. It is shown that the roles of these forces vary with flow regimes. A general phase diagram in terms of these forces is proposed to describe the flow regimes in horizontal pneumatic conveying. © 2011 American Institute of Chemical Engineers AIChE J, 2011

Micromechanic modeling and analysis of the flow regimes in horizontal pneumatic conveying

The effect of a bend on the particle cross-section concentration and segregation in pneumatic conveying systems

The results of numerical modeling of horizontal pneumatic conveying of polyethylene pellets are presented. Two different techniques have been applied to track the particle trajectories: discrete element method (DEM) and discrete particle model (DPM). Particle-particle and particle-wall collisions in DEM are treated using a soft-spheres approach. In contrast, a hard-spheres modeling of particle-wall interactions is realized in DPM. The unsteady numerical calculations simulated the behavior of particles in a wide range of flow regimes, beginning from dilute and ending with dense particle flows. The advantages of DPM are fast computations and reduced requirements of computer resources owing to larger time step and smaller amount of stored information than DEM. However, the results of calculations show that DPM is more appropriate for modeling of dilute particle flow (particle volume fraction less than 10%), whereas the DEM approach can be successfully utilized for simulation of various flow regimes between l...

Thomas Mooney

Papers

A comparison of analytical and numerical models with experimental data for gas-solid flow through a straight pipe at different inclinations