Computer simulations of critical, non-stationary granular flow through a hopper Original Research Article

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 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, β = 1. This exponent may be universal, but our present simulations can reach no definite conclusion on this point.