2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/28454Evolution of mixing of granular solids in a slowly rotated 2D drum is considered as a discrete mapping. The rotation is around the axis of the upright drum which is filled partially, and the mixing occurs only at a free surface of a material. The most simple cases that demonstrate clearly the essence of such a type of mixing are studied analytically. We calculate the characteristic time of the mixing and the distribution of the mixed material over the drum.11 pages (epsf-LaTeX) and 8 EPS figuresCondensed MatterChaotic DynamicsMathematical PhysicsPattern Formation and Solitonstext