COMPUTER-SIMULATIONS OF CRITICAL, NONSTATIONARY GRANULAR FLOW-THROUGH A HOPPER

Computer simulations based upon molecular dynamics techniques are used to study the case of a granular material consisting of non-spherical particles flowing through a collimating hopper. In these simulations we identify four generic flow regimes which depend upon the rate at which material flows into the hopper: (A) The outflow rate is steady and relatively unaffected even when there are large fluctuations in the inflow rate; (B) the outflow is steady, but the hopper can clog given sufficiently large fluctuations in the inflow rate; (C) the outflow varies with time and the mean time to clogging is nonzero, hence, even in the absence of fluctuations the hopper will eventually clog; and (D) The outflow is unsteady and the hopper is always clogged. Region C defines the critical flow regime, with flow exponent, beta = 1. This exponent may be universal, but our present simulations can reach no definite conclusion on this point.