Mixing grains using flux through a galton board

BENITO, J. G.; A. M. VIDALES; I. IPPOLITO

Mendoza, Argentina

Otro; IX Reunión Internacional Sobre Recientes Avances en Física y Mecánica de Fluidos; 2006

Universidad Nacional de Cuyo - Facultad de Ingeniería

We present an experimental and numerical study concerning the problem of the passage of small particles of different species through a Galton Board, i.e., a two dimensional array of equally spaced obstacles arranged to form a triangular lattice. The aim of the present paper is to characterize the mixture of particles at the exit as a function of the separation between the lateral walls of the board. To perform experiments, the board is placed vertically and small disks of two different species are launched from above. The relative separation between lateral walls can be varied as wanted. Disks fall down because of gravity effects, colliding successively with obstacles and, eventually, with lateral walls. When they finally get the exit at the bottom of the board, they are collected in separate boxes, depending on their final horizontal positions. Separation between walls is varied and the exit distribution of particles and their degree of mixture are calculated as a function of separation. Simulations are performed in a similar way, trying to follow the main features of experiments. Only geometrical aspects are consider and no dynamic calculations are used. We found that there exists a crossover from a Gaussian-like to a uniform-like behaviour when the separation between walls is less than a critical value. This is a crucial point to consider in mixing particles. A systematic study of this crossover is performed through numerical simulations and the results are also approximated by a theoretical model of the problem. A criterion to mix particles with this procedure is established and conclusions for applications are drawn.