Powder mixers require blades to mix powders of different kinds by way of imparting convective motion to the powder particles. Mixing performances of complex mixers such as cylindrical vertical mixers and ribbon mixers have been studied both by experiments and DEM simulations, and mechanisms responsible for the mixing have been identified to some extent. In this work, we focus on the mixing of particles by a single blade that moves through a bed of particles (of 2 mm dia.) on a horizontal plane, and establish mixing mechanisms when the blade rake angle varies between 60° to 135° at a fixed blade speed of 0.2 m/s by using DEM simulations. The DEM simulation results are verified by comparing them with the measurements in the literature. We quantify the forces on the blade as a function of blade rake angle and speed, and examine the possibility of using these force relationships to estimate the torque on a pair of blades in a vertical-axis bladed mixer, for which DEM simulation results are available. We will further examine the nature of dynamic similarity of the particle flows in two cases when their Froude numbers are matched; Froude number is defined as Sqrt[u^2/(gd)], where u is the blade speed, d the particle diameter and g the acceleration of gravity. Such a similarity principle could be useful when scaling mixer dimensions.
Keywords: DEM simulations, Mixing, Horizontal particle bed.