Intermittent granular flow in the presence of an electric field
Center for Condensed Matter Physics & Institute of Physics
Chinese Academy of Sciences - Beijing 100080, PRC
2 Nonlinear Physics Group, Department of Physics, San Jose State University San Jose, CA 95192-0106, USA
Accepted: 22 August 2001
In this letter experimental observations of vertical-pipe granular flow in the presence of an electric field are reported. Granular nickel particles flowing down a vertical pipe are found to be retarded by a local horizontal ac electric field when the field voltage V is greater than a critical voltage Vc. For , the steady-state flow rate is practically unaffected by V. The flow rate decreases discontinuously at Vc, and then decreases gradually for . Physically, particle clusters are formed above an arch interface, which exists in the electric-field region when . The vertical flow consists of clusters intermittently dropping off from the interface. A transient density wave with wavelength lengthened by electric field is also observed.
PACS: 45.70.-n – Granular systems / 97.10.Ld – Magnetic and electric fields; polarization of starlight
© EDP Sciences, 2001