We experimentally investigate the avalanche statistics of dry granular materials in a slowly rotating drum for five types of beads with varied surface roughness.For all beads,two distinct angles,i.e.,repose angleθr a...We experimentally investigate the avalanche statistics of dry granular materials in a slowly rotating drum for five types of beads with varied surface roughness.For all beads,two distinct angles,i.e.,repose angleθr and maximal angleθm,can be clearly defined,and the avalanche size distributions P(δθ)are Gaussian-like.θr,θm,and the span in P(δθ)are all positively correlated with bead surface roughness.This observation thus contrasts with a power-law P(δθ)predicted by self-organized criticality,but is reminiscent of a first-order phase transition.We speculate that both the inertia effect and the velocity-weakening mechanism during an avalanche process can enhance the first-order features,which are however absent in plasticity of sheared amorphous solids.We also discuss the dependence betweenθr andθm for various particles,as well as the correlation between starting and stopping angles for an individual avalanche.展开更多
基金support from the fellowship of China Postdoctoral Science Foundation(2021M702151)This work was supported by the National Natural Science Foundation of China(11974240)the Science and Technology Commission of Shanghai Municipality(22YF1419900).
文摘We experimentally investigate the avalanche statistics of dry granular materials in a slowly rotating drum for five types of beads with varied surface roughness.For all beads,two distinct angles,i.e.,repose angleθr and maximal angleθm,can be clearly defined,and the avalanche size distributions P(δθ)are Gaussian-like.θr,θm,and the span in P(δθ)are all positively correlated with bead surface roughness.This observation thus contrasts with a power-law P(δθ)predicted by self-organized criticality,but is reminiscent of a first-order phase transition.We speculate that both the inertia effect and the velocity-weakening mechanism during an avalanche process can enhance the first-order features,which are however absent in plasticity of sheared amorphous solids.We also discuss the dependence betweenθr andθm for various particles,as well as the correlation between starting and stopping angles for an individual avalanche.
