The influence of driving conditions on flow behavior in sheared granular flows

Bottom wall friction coefficients on the dynamic properties of sheared granular flows

“…the particles that occupied the shear cell, as can be seen from the top view, and A s was the entire area of the shear cell base [5]. To generate sufficient shear in the flow field, a layer of 3-mm glass beads was glued to the surfaces of the inner and outer walls.…”

“…A capture speed of 500 FPS and with a resolution of 1200 × 400 pixels was used, and all images were taken after the system had been shearing for at least 1 min to ensure a steady state of the flow field. The particle tracking velocimetry technique was used to calculate the velocity of the beads by locating their centers in the high-speed images and determining their displacements between two consecutive images [5,14,27].…”

“…The local area solid fraction in each radial region can be determined as follows v i = A pi / A si , where A pi was the cross-sectional area of the particles that occupied the radial region i and A si was the area of the radial region i [5,21,26]. The ensemble averages of the tangential bV θ N and radial bV r N velocities in each radial region were obtained from approximately 1200 particles, as follows:…”

“…The slip velocity at the driving wall was determined using the following equation based on previous studies [5,21,26]:…”

“…Therefore, a solid-like region and a liquid-like region (shear band region) can coexist in the same flow system. The thickness of a shear band is approximately four to ten particle diameters, which depends on the external driving conditions, solid fraction, and interstitial fluid viscosity [1][2][3][4][5]. The interactive collisions that occur between particles cause the random motions of these particles, which become the dominant mechanism influencing flow behavior in granular materials [6,7].…”