Rheological response of granular materials under dynamic conditions

Abstract

The rheological behaviour of a dense granular bed under dynamic conditions is investigated by simulating granular flow in the FT4 powder rheometer using the Discrete Element Method. The distribution of the prevailing stresses and strain rates in the granular bed, and their dependence on material properties and blade operational conditions, are analysed. The shear stress was found to be approximately constant in the radial direction along the blade but dissipates in the circumferential direction away from the blade. Analogously, the strain rate decreases with increasing angular distance away from the blade as the bed becomes less dynamic. An increase in the blade tip speed, particle aspect ratio and interfacial energy results in an increase in the average shear stress in the granular bed. A predictive model is proposed to compute the average shear stress in the granular bed based on the blade torque by considering the effects of blade tip speed, particle aspect ratio and interfacial energy.