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Granular flows through vertical pipes controlled by an electric field.
1Center for Condensed Matter Physics & Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China.
Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
|December 12, 2001
Summary
An AC electric field influences granular nickel particle flow in vertical pipes. Two flow behaviors emerge based on voltage, affecting flow rates and particle origin, demonstrating a competition between electric field blocking and gravity.
Area of Science:
- Granular physics
- Electrorheology
- Particle flow dynamics
Background:
- Understanding granular material flow is crucial in various industrial processes.
- The influence of external fields, such as electric fields, on granular media is an active area of research.
- Previous studies have explored electric field effects on particle behavior, but specific investigations into horizontal AC fields on vertical granular flow are less common.
Purpose of the Study:
- To experimentally investigate the effect of a local, horizontal alternating current (AC) electric field on the flow of granular nickel particles in a vertical pipe.
- To characterize the flow rate as a function of applied voltage and time.
- To elucidate the distinct flow regimes and their underlying mechanisms.
Main Methods:
- Granular nickel particles were flowed down a vertical pipe from a hopper.
- A horizontal AC electric field was applied locally within the pipe.
- Particle mass flow rate was measured over time using an electronic balance for various applied voltages.
Main Results:
- Two distinct flow behaviors were observed depending on the electric field magnitude (voltage V).
- Below a critical voltage (V(c) = 2.0 kV), a downward-moving interface appeared, leading to two flow rates (Q(A2) and Q(B)) with distinct particle origins.
- Above or at V(c), the interface vanished, resulting in a single, constant flow rate (Q(A2)). The Q(A2) flow rate decreased with increasing voltage (power law exponent -0.8), while Q(B) was voltage-independent.
Conclusions:
- The applied AC electric field significantly alters granular flow dynamics by competing with gravity.
- The electric field effectively impedes dense particle columns but is less effective on dilute ones.
- The observed flow behaviors are a direct consequence of the interplay between the electric field's blocking effect and the hopper's gravity-driven pushing force.