Numerical computation of turbulent gas-solid particle flow in a 90° bend

CFD Investigation into the Effects of Surrounding Particle Location on the Drag Coefficient

In the simulation of dilute gas-solid flows such as those seen in many industrial applications, the Lagrangian Particle Tracking method is used to track packets of individual particles through a converged fluid field. In the tracking of these particles, the most dominant forces acting upon the particles are those of gravity and drag. In order to accurately predict particle motion, the determination of the aforementioned forces become of the upmost importance, and hence an improved drag force formula was developed to incorporate the effects of particle concentration and particle Reynolds number. The present CFD study examines the individual effects of particles located both perpendicular and parallel to the flow direction, as well as the effect of a particle entrain within an infinite matrix of evenly distributed particles. Results show that neighbouring particles perpendicular to the flow (Model 2) have an effect of increasing the drag force at close separation distances, but this becomes negligible between 5–10 particle diameters depending on particle Reynolds number (Rep). When entrained in an infinite line of particles co-aligned with the flow (Model 1), the drag force is remarkably reduced at close separation distances and increases as the distance increases. The results of the infinite matrix of particles (Model 3) show that, although not apparent in the individual model, the effect of side particles is experienced many particle diameters downstream.

Numerical investigation of indoor particulate contaminant transport using the Eulerian-Eulerian and Eulerian-Lagrangian two-phase flow models

Transport of micron particles in a displacement ventilated room was simulated using both the Eulerian-Eulerian model and the Eulerian-Lagrangian model. The same inter-phase action mechanisms were included in both models. The models were compared against each other in the aspects of air velocity, particle concentration, and particle-wall interactions. It was found that the two models have similar accuracy in predicting the airflow field while each of them has its own advantage and drawback in modelling particle concentration and particle-wall interactions. The E-E model is capable of providing a mechanistic description of the inter-phase interactions, whilst the E-L model has obvious advantage in modelling particle-wall interactions. Advices were given for choosing an appropriate model for modelling particulate contaminant transport in indoor environments.