Using DEM in Particulate Flow Simulations

Abstract

There is no doubt that the dynamics of solid particles is the center of interest in the mineral processing industry, including crushing, grinding, classification, mineral separation, and leaching, just to name a few. But most processes involve fluid as a carrier and/or media, making the study of fluid dynamics and coupling between fluid dynamics and particle motion essential part for such a particulate flow. Various modeling and coupling approaches capable of considering particle behaviors, fluid dynamics and coupling effects, have been actively pursued, researched and developed in recent years. By name, particulate flows usually include one or more continuous fluid phase, and one or more type of particles, or say generally, discrete phases. The discrete particles/bubbles/ droplets are often dispersed in a continuous phase, so a discrete phase is also called a disperse phase in continuummultiphase modeling. There may be strong interactions between discrete phases and continuous phase, and strong interactions among discrete phases for dense particulate flows. The coupling physics pose a huge challenge to researchers, since coupling physics between fluid dynamics and particle motion requires coupling numerical modeling approaches. There is no one-fits-all solution for all applications especially after considering limitations, accuracy, computational costs of various numerical models. As computer technology for hardware and software advances so rapidly, it also push scientific and engineering simulations to high standards of requirement with respects to accuracy, fidelity, efficiency. There is increasing research activity of using Discrete Element Method (DEM) in particulate flow simulations. Discrete Element Method (DEM) (Cundall & Strack, 1979; Landry et al., 2003; Walton, 1992) is a Lagrangian model and is well accepted nowadays to model solid particle behavior. In principle, the DEM is based on the concept that individual particles, each of which is usually assumed to be semi-rigid, are considered to be separate and are connected at boundaries by appropriate contact laws. DEM naturally captures characteristics of each particle, therefore further dynamics like breakage and wear can be modeled locally at the small scale. Using DEM to track dynamics of particles, although the computing cost is high, eliminates the need of modeling fluid dynamics of particle phase, therefore improves fidelity of simulations. Interactions among discrete phases can be addressed more accurately inside DEM, thank to that microscopic physics has been clearly understood and described at most times. 2