Tangential velocity profiles of granular material within horizontal rotating cylinders modelled using the DEM

Abstract

Flow regimes of granular materials in horizontal rotating cylinders are industrially important since they have a strong influence on the rates of heat and mass transfer within these systems. The tangential velocity profile, which describes how the average particle velocity in the direction parallel to the surface of the bed varies along a radius perpendicular to the surface of the bed, has been examined for many experimental and simulated systems. This paper is concerned with tangential velocity profiles within rotating cylinders simulated using the discrete element method. For high fill levels good agreement is found between the simulated velocity profiles and the equation proposed by Nakagawa et al. (Exp Fluids 16:54-60, 1993) based on magnetic resonance measurements. At lower fill levels slip is observed between the cylinder wall and the particles in contact with it and also between the outer layer of particles and the bulk of the bed. It is demonstrated that this slip occurs when the particles in contact with the wall are able to rotate and that it may be prevented either by using non-spherical particles or by attaching "lifters" to the cylinder wall.

Is axial dispersion within rotating cylinders governed by the Froude number?

“…The fill level is defined as the fraction of the cylinder taken up by particles and voids between particles when the cylinder is rotating. The cylinder in which the particles are rotated is modeled as a smooth, but frictional, cylinder onto which "wall rougheners" have been attached to prevent slip between the cylinder wall and the bed [17]. The wall rougheners consist of lines of 3 mm particles running along the length of the cylinder and they are equally spaced around the cylinder circumference with a center-to-center spacing of approximately five particle diameters.…”

DEM study of granular flow characteristics in the active and passive regions of a three‐dimensional rotating drum

“…Due to the dominance of collisions and significant shear in the rotating drum, particle‐particle interactions have to be treated carefully and accurately. Past DEM studies focusing on the solid motion in the rotating drum have provided more understanding on various phenomena, including mixing and segregation, axial transport and dispersion, heat‐transfer behavior, solid circulation time, tangential velocity profile, onset mechanism of axial band, and particle dynamics …”

Validation of a lattice Boltzmann model for gas–solid reactions with experiments

“…9 reveals that plots of q CO against z are not smoothly decaying functions, but rather display stair-stepped oscillations at the start of the bed with a period consistent with the length a single particle. Owing to the initialisation procedure which relied on dropping sheets of spheres into a tube with a discrete particle model [51], the z coordinate for the centres of spheres is regular at the start of the packing but becomes increasingly random with increasing z. Thus, oscillations in concentration are a result of residence times.…”

“…5(a). The position of the particles was determined from a discrete particle model [51] by dropping sheets of spheres into a cylinder and tapping. Fig.…”