Effects of horizontal vibration on hopper flows of granular materials

The current experiments investigate the discharge of glass spheres in a pla nar wedge-shaped hopper (45 degrees sidewalls) that is vibrated horizontall y. When the hopper is discharged without vibration, the discharge occurs as a funnel flow, with the material exiting the central region of the hopper and stagnant material along the sides. With horizontal vibration, the disch arge rate increases with the velocity of vibration as compared with the dis charge rate without vibration. For a certain range of acceleration paramete rs (20-35 Hz and accelerations greater than about 1 g), the discharge of th e material occurs in an inverted-funnel pattern, with the material along th e sides exiting first, followed by the material in the core; the free surfa ce shows a peak at the center of the hopper with the free surface particles avalanching from the center toward the sides. During the deceleration phas e of a vibration cycle, particles all along the trailing or low-pressure wa ll separate from the surface and fall under gravity for a short period befo re reconnecting the hopper. For lower frequencies (5 and 10 Hz), the free s urface remains horizontal and the material appears to discharge uniformly f rom the hopper. (C) 1999 American Institute of Physics. [S1070-6631(99)0220 1-1].