On the calculation of self-diffusion in vertically agitated granular beds

We present self-diffusion calculations derived from discrete element simulations of an idealized granular material under gravity, which is energized through vertical, sinusoidal oscillations of a plane rigid floor. The bed of particles is agitated to a degree so that computed steady-state profiles of granular temperature and solids fraction are consistent with kinetic theory predictions. The average self-diffusivity for the entire assembly, computed both from the velocity autocorrelation function and the mean-square displacement, is found to compare well with an analytic expression taken from kinetic theory.

Graphical abstractThe self-diffusivity of a vertically oscillated ideal granular material was determined from discrete element simulations. The bed of inelastic, frictional spheres was agitated to a degree so that computed steady-state profiles of granular temperature and solids fraction were consistent with kinetic theory predictions. In this situation, the average self-diffusivity for the assembly (see Fig.) compared well with an analytic expression taken from kinetic theory.Figure optionsDownload full-size imageDownload as PowerPoint slide