Significance of Chute-Related Factors on Segregation of a Gr anular Chute Flow

Granular segregation is a common occurrence in the pharmaceutical and food industries, although typically it is unde sirable as segregation leads to non-uniformity in end products and t hus lowers the overall product quality. It is well-known that se gr gation occurs due to differences in the species composing th e mixture such as particle size, shape or density; unfortunat ely, this is often an unchangeable quality. The question is then h ow to minimize (or enhance, depending on the application) the s egregation, given a mixture that cannot be changed; thus, the f ocus of this work is on external factors that can be controlled . Specifically, considering a dry granular chute flow, we focus on chute-related factors such as the inclination angle, sur face roughness, fill volume, cross-sectional profile, and base pr ofile of the chute. We present here, the investigation results (to date) into some of these factors, for a mixture comprising tw o species of different size. The numerical simulations were c onducted using the discrete element method (DEM) specifically using the open-source code LIGGGHTS developed for granular simulations. A small-scale table-top experiment consisti ng of an acrylic chute, approximately 1m in length with variable i nclination angle, was used to obtain results both for obtaini ng a preliminary understanding, as well as to validate the numer ical simulations. Monitoring the rate and extent of segregation when varying each investigated factor, unsurprisingly we find th at e segregation dependency is not straightforward, due to the s ensitivity of the granular flow’s velocity profile. Formulatio n of a general guideline or optimal set of conditions, will thus re quire further investigation using other granular compositions a s well. Introduction Granular materials can be seen in processing industries of f ood, pharmaceuticals, detergents, chemicals, paints, cosmeti cs, tc. During handling of these products, stirring, shaking or vib ating can cause segregation which is sometimes a problem in these industries. Segregation is the separation of different par icles in the mixture. Even if the particles are mixed initially, th e mechanical processes lead to separation that is, they separ at into clusters of similar particles based on differences in s ize, shape or density. In industries, this segregation of partic les may give rise to non-uniformity in products and ultimately affe cts the product quality. Although the root cause of segregation is differences of the particles making up the mixture, oftenti mes we have little to no control over the mixture composition. As such the overarching goal of this research is to study how the segregation process can be affected by external parameters such as the inclination of the chute transporting the chute, as th is affects the flow velocity and therefore the segregation, indir ectly. Segregation aside, the flow of granular particles have been s tudied widely through both numerical and physical experiments . Bi et al. [2] investigated experimentally the influence of bo ttom roughness on monodisperse disks flowing down an inclined chute. They studied the positions, velocities, and rotatio ns with respect to different inclinations. Tai and Lin [16] present ed results of granular flow in an inclined chute into the horizonta l run-out zone. They studied the motion of granular masses and 1m 0.3m