(303a) Simulating a Chute Flow Segregation Tester

Bhattacharya, T., University of Pittsburgh
McCarthy, J. J., University of Pittsburgh

Handling of granular materials inevitably involves the application of many solids processing devices such as hoppers, chutes, mixers or other transfer equipment. Granular materials, however, segregate if they are subjected to flow or external agitation in the presence of a gravitational field. Many studies of granular flow have focused on gravity driven chute flows owing to its practical importance in granular transportation and to the fact that the relative simplicity of this type of flow allows for development and testing of new theories/equipment. In the present work, we observe the deposition behavior of both, mono-sized and poly-dispersed dry granular materials in an inclined chute flow. The effects of different parameters such as chute angle, particle size, falling height and charge amount on the mass fraction distribution of granular materials after deposition are investigated. The simulation results obtained using the discrete element method (DEM) are compared with the experimental findings and a high degree of agreement is observed. Tuning of the underlying contact force parameters allows realistic results and is used as a means of validating the model against available experimental data. The tuned model is then used to find the critical chute length for segregation based on a recently proposed theory by our group. As per the theory, segregation can be eliminated if a flow is perturbed above a critical forcing frequency via periodic flow inversion. This critical frequency, f , is inversely proportional to the characteristic time of segregation, ts . Mixing is observed instead of segregation when L Uavg ts , where L , Uavg , and ts denote the length of the chute, the average stream-wise flow velocity of the particles, and the characteristic time of segregation, respectively.