Discharge oscillation of parti- cles from a vertical pipe with capillary outlet
Discharge oscillation of particles from a vertical pipe with capillary outlet

A new style of discharge process from a vertical open-top pipe with capillary outlet is reported. The outflux fluctuates greatly with time and the bulk condensed granular flow in the pipe shows stop-and-go motion when the filling height is above a threshold. When the filling height falls to- wards the threshold, led by a transitional stage, the outflux and the bulk movement become much stable. The upper surface dropping velocity variation is measured. A heuristic theory is proposed to understand the stop-and-go motion and the transitional behavior.