EXPERIMENTAL-EVIDENCE OF DENSITY-FLUCTUATIONS IN 2-DIMENSIONAL BINS

We have found experimentally the existence of random density fluctuati ons, during the discharge of monodisperse granular material from flat bins, which follows a 1/f(alpha) noise, where alpha similar or equal t o 1.32 just above, and alpha similar or equal to 1.0 just below the ex it of the bin. The corresponding rescaled range analysis for the fract al noise obtained just above the exit gives a Hurst parameter H simila r or equal to 0.16, and a fractal dimension D similar or equal to 1.84 .