ISSN:
1077-3118
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Granular flow of nickel particles down a vertical pipe from a hopper is shown to be retarded by a horizontal ac electric field applied to a local region along the pipe. The particles are released from the hopper by pulling out a stopper in the hopper. Two sequences of experiments with different initial flow conditions are performed. In the first sequence, a dilute flow in the pipe is created after a fixed voltage V (≤4.8 kV) is applied across two short, vertical copper electrodes. The steady-state flow rate Q remains practically constant for V〈V1 (=2.6 kV). At V=V1, Q drops abruptly; the drop depends on the location of the electrodes. For V〉V1, the flow becomes dense; Q decreases with a power law, Q∼V−1. In the second sequence of experiments, V is first set at 4.8 kV; the flow is allowed to start, and soon becomes a dense flow; then, V is reduced to the desired voltage. The new, steady-state Q vs V curve coincides with the previous Q(V) curve of the first sequence, except for V2〈V〈V1, where V2=1.0 kV. The voltage V2 is a continuous transition point at which Q changes from a dense flow (V〉V2) to a dilute flow (V〈V2). Our results show that a large enough ac electric field can decrease the flow rate of a dilute or dense flow; the critical voltage that can reduce a dense flow, V2, is less than that for the dilute flow, V1. © 2002 American Institute of Physics.Acknow
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1459767
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