Discrete element simulation of free flowing grains in a four‐bladed mixer

Abstract

Numerical simulations of granular flow in a cylindrical vessel agitated by a fourblade impeller were performed using the discrete element method. Velocity, density, and stress profiles within the mixer displayed a periodic behavior with a fluctuation frequency equal to that of the blade rotation. Blade orientation was found to affect flow patterns and mixing kinetics. For an obtuse blade pitch orientation, a threedimensional recirculation zone develops in-front of the blade due to formation of heaps where the blades are present. This flow pattern promotes vertical and radial mixing. No recirculation zone was observed when the blade orientation was changed to an acute blade pitch. The system's frictional characteristics are shown to strongly influence the granular behavior within the mixer. At low friction coefficients, the 3-D recirculation in front of the obtuse blade is not present reducing convective mixing. Higher friction coefficients lead to an increase in granular temperature which is associated with an increase in diffusive mixing. Normal and shear stresses were found to vary with mixer height with maximum values near the bottom plate. Additionally, a strong dependence between the magnitude of the shear stresses and the friction coefficient of the particles was found. The stress tensor characteristics indicate that the granular flow in our simulations occurs in the quasi-static regime. At the same time, the averaged pressure was found to vary linearly with bed height and could be predicted by a simple hydrostatic approximation. V

Analysis of powder rheometry of FT4: Effect of air flow

“…1(c). Similar to the method suggested by Remy et al (2009) and Hare et al (2015 the measurement cell size is about 5-6 particle diameter. Based on the velocity gradient of particles, the strain rate in the measurement cells is given as:…”

“…Based on experiments and CFD simulations, Khalilitehrani et al (2013;2015) studied the rheology of dense granular flows in a disc impeller high shear granulator. Remy et al (2009Remy et al ( , 2011 carried out stress analyses of particle flow in a rotating blade mixer using DEM. They found that the normal and shear stresses were affected by the degree of polydispersity of particle size, and the shear stress was sensitive to the particle friction coefficient.…”

Applications of Discrete Element Method in Modeling of Grain Postharvest Operations

“…The process uses Newton's laws of motion that gives 159 the relationship between the particle motion and forces acting on each particle. Translational and 160 rotational motions of a particle are defined as (Remy et al 2009 …”

Analyzing the Mixing Dynamics of an Industrial Batch Bin Blender via Discrete Element Modeling Method

“…Fine tuning of the values of Poisson's ratio and Young's modulus is important because it decides the stiffness of the particles, which on the other hand controls the particle deformation or overlap upon contact. It is suggested that the particle overlap be controlled so that the model stays within the elastic limit [14].…”