Density fluctuations during the discharge of granular material from a two-dimensional bin

Abstract

We have found experimentally the existence of strong density fluctuations (density waves) during the discharge of monodisperse granular material from vertical flat bins. These density waves follow, approximately, a 1/f(alpha) fractal noise, where alpha = 1.32, just above the exit of the bin and, a 1/f noise, just below the exit. The corresponding rescaled range analysis (Mandelbrot-Van Ness fractional Brownian motion) for the fractal noise gives a Hurst parameter H = 0.16 and a fractal dimension D = 1.84.