Using new Refractive Index Matching material to investigate length scale effect of irregular sand particles in slumping regime in a rotating drum.

Granular flows in the slumping regime of a rotation drum are commonly applied to study the mechanism of geophysical flow, particularly in landslides and avalanches. In previous studies, the trigger mechanism with the irregular particle were well investigated but how character length effects are not entirely understood. In this study, we would like to understand how length scale influence the intermittent avalanches by studying the experiments in two different size drums in the slowly rotational speed (slumping regime). To gain optical access to the interior and perimeter, we use the refractive index matching material (irregular-shaped fused quartz and a blend of white mineral oils) to visualize and measure the internal structure. The motion of the particles is captured through a high-speed camera with Particle Tracking Velocimetry (PTV) technique. The study suggests the possible distributions of the slumping frequency, the flow area, and the character of the topping slope by varying the rotational speed, the drum diameters, and the filled rate.