The influence of particle shape on the granular rheology of dense granular flow

Erosion is a common natural phenomenon on earth. External forces, such as gravity and streams, can drive the particle-fluid flows as a moving layer and influence the surrounded landscape's evolution. To understand the dynamic of granular flow, adopting an appropriate rheological model is crucially important. In previous research, the rheology models were developed and tested with the regular shape of the particles (e.g., spherical particles). However, the effects of irregular-shaped particles are poorly studied.We acquire the interior measurement of the granular motions by employing laser illumination, fluorescent dye, seeding particles, and a high-speed camera. We use aqueous glycerin and irregular fused quartz sand (Refractive Index Matching material set) to achieve optical assessable granular flow. We performed the experiments with a tilting rectangular tube (40 to 50 degrees) and applied a stationary upward flow by a well-controlled gear pump.We used two methods to measure the flow velocity field, Particle Tracking Velocimetry (PTV) and Particle Image Velocimetry (PIV). For the PTV analysis, we used the algorithm of Active Contour to precisely capture the center of the irregular particles and track their motion. We first compare the differences between the PIV and PTV results and then use those results to compare with the existing rheological model predictions.