Experimental study on the mechanism of convection modes in vibrated granular beds

This paper describes a mechanism of the newly found convection mode of vibrated granular beds which gives rise to multi-pairs of convection rolls. In beds of glass beads with mean diameters d less than or equal to 0.5 mm, neither the ambient air pressure nor vessel materials significantly affect the critical vibrational acceleration above which the convection mode changes. Measurements of air pressure within vibrating granular beds at two locations, near the side wall and in the middle of the bed, show different period-doubling bifurcations. There are differences in the phase and the magnitude of pressures between the two measured points. On the basis of these experimental findings we propose mechanisms for two convection modes in vibrated granular beds.