Granular boycott effect: How to mix granulates

Granular material can display the basic features of the Boycott effect in s edimentation. A simple experiment shows that granular material falls faster in an inclined tube than in a vertical tube, in analogy with the Boycott e ffect. As long as the inclination of the tube is above the avalanche thresh old, descent of granular material in the tube causes internal convection wh ich in turn results in an efficient mixture of the granular components. By contrast, as in analogous experiments in two dimensions, a vertical fall of granular material occurs via successive block fragmentation, resulting in poor mixing. [S1063-651X(99)02209-6].