Power-law flow statistics in anisometric (wedge) hoppers

We find the probability for N particles to exit an anisometric ( having unequal dimensions) hopper before jamming to have a broad power-law decay with exponent alpha = -2, in marked contrast to the exponential decay seen in hoppers with symmetric apertures. The transition from exponential to power law is explained by amodel that assumes particle motion is correlated over a distinct length scale. Hoppers with lengths larger than this length are modeled as a series of adjacent, statistically independent "cells." Experiments with apertures 27-37 particle diameters D long are well fit by a three-cell model, implying that the correlation length is approximate to 9-12D.