A cellular automaton for grains in a rotating drum

We propose a generalization of the cellular automaton model introduced rece ntly by Lai, Jia and Chan [Phys. Rev. Lett. 79 (1997) 4994] for simulating friction induced segregation in a rotating drum. We use our model to invest igate geometrical properties of mixing and segregation. Simulations of the model reproduce recent experimental results on mixing efficiency and sponta neous stratification. We also make two predictions - for the dependence of the mixing rate on the speed of rotation and for the stratification of gran ular system in the drum which is less than half filled. (C) 1999 Elsevier S cience B.V. All rights reserved.