Surface Instability And Transport Of Granular Particles In A Vertically Shaken U-tube

Liquid in a U-tube always automatically balances to the same height in both two columns, but it is totally different in a vibrofluidized granular system. When a granular material fills a U-tube which is vibrated vertically, the column of gains in one branch of the tube grows while the other one falls, so the symmetry between left and right is broken. The large height difference of the level of grains will remain when the vibration is stopped.This phenomenon called surface instability.Most researches of surface instability and transport of granular particles in a U-tube focused on the three-dimensional situation, physical properties of particles and geometrical characteristics of the container, as well as vibration conditions were made a careful study.But in previous studies, no one noticed how the length of the channel at the bottom affects the transport, and two dimensional experiment is also rarely involved. In two-dimensional containers, the behavior of each particle can be observed clearly, and the height difference of the two columns can be measured more accurately. This paper mainly studies the surface instability and transport of granular particles in a two dimensional U-tube. We study the evolution of the height difference between the columns of grains in the branches of the tube,explore the effect of the initial state, the number of particles and the channel length on the system variables.Experiments are recorded by a high speed camera. First, we fixed the total number of particles to explore the evolution of the height difference and the influence of the initial state, it can be said that the surface level instability is not due to its sensitivity to the initial conditions. Secondly, given fixed initial condition, we change the number of particles, and define a parameter)N+/(N|N-N=|LRLR? to describe the height difference. The result shows parameter ? grows with the particle number. Finally, we change the channel length to obtain the relationship of N-? curves under different channel length, founding that too short channels can cause big swings in parameter over time, and long channels are advantageous to parametric stability.