Structural relaxation and avalanche dynamics of particle piles under vertical vibration

Granular matter can exhibit solid or liquid behavior,which contains complex physical mechanisms.In this work,we experimentally investigated the structural relaxation and avalanche dynamics of particle piles under vertical vibration.The influence of vibration parameters on the avalanche process was studied.The morphological features of avalanches were recorded and classified using high-speed camera.The effects of vibration parameters and particle properties on the relaxation mode are obtained.It is found that the evolution of particle pile height with time can be described by an exponential decay function.The relaxation rate and avalanche characteristics of four types of particles with different sizes are discussed.At the same acceleration level,for two larger particles,a smaller amplitude(A=0.025 mm)leads to a faster relaxation rate,while for two smaller particles,a large amplitude(A=0.500 mm)leads to a faster relaxation rate.The analogy powder surface tension is introduced to address the cohesion and flowability evolution of particles under vibration.