(341b) Segregation of Fine and Cohesive Particles

Great strides have been made in understanding and predicting size-segregation in flows of non-cohesive particles with size ratios R < 3. Extending these advances to cohesive particles and larger size ratios (fine particles) is difficult because of experimental and simulation challenges as well as the wide range of possible particle properties and flow conditions. Here we report preliminary results from DEM simulations for size-bidisperse cohesive particles and for non-cohesive fine particles with size ratios as large as R = 40. The usual segregation pattern in heap flow of small particles depositing on the upstream portion of a heap and large particles depositing further downstream occurs for low cohesion between particles for R = 2. When the cohesion is increased while maintaining the same feed rate, alternating layers of large and small particles result due to intermittent flow down the heap. Higher levels of cohesion prevent segregation. In general, the flow and segregation behavior are determined by the ratios of the cohesive force to the particle weight and to the flow-related shear force. Furthermore, the relative strengths of large-large, small-large, and small-small particle cohesive interactions must be considered. For large size ratios without cohesion, the segregation or lack thereof, in a static large particle bed under gravity depends on a complex combination of size ratio, flow conditions, particularly the magnitude of the small particle velocity fluctuations, and particle properties, including the friction and restitution coefficients. Nevertheless, we have been able to determine scalings that account for these various conditions. This material is partially based upon work supported by the National Science Foundation under Grant CBET-2203703.