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The structural properties of particulate matter can significantly affect the rheology of the system. We report the structural evolution and flow properties of dense granular flows induced by Couette shear and try to reveal the relationship between them. In unidirectional shear, monodisperse particles undergo a transformation from disorder to order. Throughout this continuous process, both the velocity and shear strain rate of the particles experience alterations. By filling with particles of varying polydispersity, the structural potential of the system can be controlled, thereby influencing the extent of structural transformations. The results indicate that the transition in flow characteristics is suppressed as the initial filling in the system approaches from high to low structural potential. The results based on the local volume fraction and relative positions of particles suggest that it is due to the weakening of the structural thinning effect caused by order. We found that both fixed shear paths and more rotatable local structures caused a significant reduction in the contact force to transfer energy. Inertia number and apparent viscosity vary with volume fraction, indicating a transition in dense granular flow after volume fraction φ≳ 0.62, with the onset of significant structural thinning effects. We have revealed the physical mechanisms influencing fluidity from a local structural perspective and established the relationship between fluidity g and φ in the continuous process of unsteady flow.
Bai et al. (Wed,) studied this question.