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.