Avalanche Merging and Continuous Flow in a Sandpile Model

A dynamical transition separating intermittent and continuous flow is observed in a sandpile model, with scaling functions relating the transport behaviors between the regimes. The width of the active zone diverges with system size in the avalanche regime but becomes very narrow for continuous flow. The change of the mean slope, $\Delta z$, on increasing the driving rate, $r$, obeys $\Delta z\sim r^{1/\theta }$. It has a nontrivial scaling behavior in the continuous flow phase with an exponent $\theta$ given, paradoxically, only in terms of exponents characterizing the avalanches $\theta =(1+z-D)/(3-D)$.