For studying the difference of diffusive characteristics between mixture and uniform particles,sets of flume experiments were conducted.The trajectories of particles with different size were extracted under various particles and hydraulic conditions by using HD camera tecnology.Dxo Viewpoint was applied on image correction,besides,displacement datas of particles were extracted by ImageJ.The relationship between the variance of displacements and time from the data was analyzed.The results showed that,firstly,particles would present different diffusion characteristics at different time scales,for different hydraulic conditions and the ranges of particles.Secondly,the diffusion characteristics of mixture particles would always tend to be ballistic movement (β=2) on large time scale,which corresponded to a sorting phenomenon resulting from the heterogeneity of particle.Thirdly,the stronger the particle’s heterogeneity,the faster sorting phenomenon occured,and lastly in the nature rivers,sorting phenomenon would be more obvious due to the much more larger scale than flume experiments.
