Insight Into Granular Flow Dynamics Relying on Basal Stress Measurements: From Experimental Flume Tests

Knowledge on the interactions between granular flows and their boundaries is essential for understanding granular flow dynamics. In this study, a series of experiments designed with different conditions were conducted using a flume configuration to investigate the granular flow behaviors and dynamics by particle image velocimetry analysis and basal normal stress measurements. The results demonstrate that the velocity profiles and depth-averaged shear rates of the granular flows significantly vary with grain size, but display insignificant changes with flow volume. For granular flows with higher content of coarse particles, high magnitude fluctuating stresses with values much greater than the mean normal stress are observed. The particle agitation of the granular flow, which is quantified by the normalized standard deviation of the fluctuating stress from the mean normal stress, exhibits a positive correlation and a negative correlation with the solid inertial stress and the equivalent friction coefficient, respectively. This indicates that the enhanced particle agitation related to the high magnitude fluctuating stress should contribute to the mobility of the granular flows. The generation of the high magnitude fluctuating stress is attributed to the high-frequency and intensive particle collisions in grain-scale, which is mainly determined by grain size. In this study, the increase of flow volume mostly resulted in an increase in the fluctuating stress related to the mean normal stress, which exhibits a minor effect on particle agitation and has no contribution toward the mobility of the granular flows.

Automated summary

Understanding the interactions between granular flows and their boundaries is crucial for comprehending the dynamics of granular flow. This study conducted a series of experiments under different conditions using a flume setup, and analyzed the granular flow behaviors and dynamics by particle image velocimetry and basal normal stress measurements. The results showed that the velocity profiles and shear rates of the granular flows varied significantly with grain size, but remained unchanged with flow volume. For flows with a higher content of coarse particles, high magnitude fluctuating stresses were observed, which were greater than the mean normal stress. The particle agitation, quantified by the normalized standard deviation of the fluctuating stress, exhibited positive and negative correlations with the solid inertial stress and equivalent friction coefficient, respectively. This suggests that the enhanced particle agitation due to high magnitude fluctuating stress contributes to the mobility of the granular flows. The generation of high magnitude fluctuating stress is attributed to the frequency and intensity of particle collisions at the grain scale, which is mainly determined by grain size. Increasing flow volume primarily led to an increase in fluctuating stress related to the mean normal stress, with minor effects on particle agitation and no contribution to the mobility of the granular flows.