Galton Board as Colliding Static Mixer

This study explores the feasibility of employing a Galton board as a static mixer for granular materials, aiming to combine energy-efficient operation with effective homogenization. Experiments with a three-dimensional (3D)-printed Galton board and steel spheres were carried out to determine key micromechanical parameters, most notably the coefficient of restitution, and to validate discrete-element method (DEM) simulations. The measured and simulated bin distributions showed strong agreement, confirmed quantitatively by chi-square and Kolmogorov–Smirnov tests, which indicated statistical indistinguishability. Parametric sensitivity analyses revealed clear trends: increasing the number of bumper rows enhanced mixing efficiency but with diminishing returns, and higher particle kinetic energy improved mixing only up to a threshold. Bumper size proved largely irrelevant except when excessively large, whereas bumper spacing strongly affected mixing quality. To account for inevitable deviations from idealized mechanics, a perturbed DEM model was introduced by randomly varying individual particle and contact properties within ±10%. These perturbations, together with naturally occurring numerical discretization effects, were shown to increase the robustness of mixing by preventing artificially symmetric outcomes. Additional trajectory tests demonstrated the chaotic sensitivity of the Galton board: even minimal perturbations of initial conditions led to substantially different final particle locations, a property advantageous for mixing. Overall, the results confirmed that static mixers inspired by the Galton board are resilient against imperfections and provide a reliable, low energy means of mixing granular materials. The findings establish validated design guidelines that can support the development of practical industrial devices based on Galton board principles.