(553g) Kinematics and Segregation of Bidisperse Granular Flow in Quasi-2D Bounded Heaps

Segregation of size bidisperse granular materials in quasi-two-dimensional (quasi-2D) bounded heap flow generates various final particle distributions which are parameter dependent. Accurate prediction of these distributions, however, requires a detailed knowledge of the flow kinematics. In this research, we first present a computational study of the kinematics of quasi-2D bounded heap flow using the discrete element method. The experimentally validated computational results reveal a universal functional form for the streamwise velocity profile for both mono- and bidisperse systems when velocities and coordinates are scaled by the local surface velocity and the local flowing layer thickness, respectively. The universal form holds true regardless of streamwise location, feed rate, particle size distribution and, most surprisingly, local particle concentration for bidisperse flows. Based on the kinematics, we develop a segregation model free of arbitrary fitting parameters that considers the interplay of advection, segregation, and diffusion. Compared with previous segregation models, excellent quantitative agreement with both experimental and simulation results is achieved. The model yields two dimensionless control parameters which depend only on the physical parameters of feed rate, particle size ratio, and system size. One, the Peclet number, captures the interplay of diffusion and advection, while the second characterizes the competition between segregation and advection. A parametric study demonstrates that final particle configurations can be controlled by properly tuning both dimensionless parameters, and the model can be readily adapted to more complicated flow geometries.