Particle-Wall Adhesion in Electropacked Beds

Electric fields applied across loosely packed beds of glass beads or sand induce strohg interparticle electrical forces. Reported here is an investigation of the closely related phenomenon of bed particles sticking electrically to wails. The yield locus of a metallic sled sliding over the surface of an electropacked bed is measured as a function of the applied electric field. The yield locus shifts with applied field because greater shear force is required to initiate movement, but the static friction coefficient remains unchanged. The effective electrical stress acting on the sled is estimated from the yield-locus shift, and the results are compared with data from other experiments, including fluidized-bed measurements and the angle-of- repose technique.