W. Cooke et al., PARTICLE-SIZE SEGREGATION IN A 2-DIMENSIONAL BED UNDERGOING VERTICAL VIBRATION, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics, 53(3), 1996, pp. 2812-2822
We present experimental results on the size-ratio and acceleration dep
endences of particle size segregation behavior for a single intruder i
n a two-dimensional bed of monodisperse particles undergoing vertical
vibration at low accelerations. Using trajectory maps based on digital
high speed photography and computer image processing we find that, at
all base accelerations, the intruder and surrounding particles move u
pwards at the same speed. The motor of such convective motion is slip
planes and block motion of particles slipping past each other which pu
sh the intruder and surrounding particles upwards in a collective moti
on. Although some of these features have been previously observed, we
use these observations to propose a mechanism for segregation at low a
ccelerations. In this the intermittent steplike motion is found to be
due to the finite frequency of slip planes and dislocations, causing t
he intruder and surrounding particles to move upwards in finite-size j
umps. The stability of the intruder is not relevant in our experiments
and no fundamental difference in mechanism between the so-called inte
rmittent and continuous regimes exists; only the frequency of slip pla
nes and block motions is important.