Sublimation of a Vibrated Granular Monolayer: Coexistence of Gas and Solid

The fluidization of a monolayer of glass beads in a horizontally and vertically vibrated annular container is studied. At peak forcing accelerations between 1.1 and 1.5 g, a solidlike and a gaslike domain coexist. The solid fraction decreases with increasing acceleration and shows hysteresis. The sharp boundaries between the two regions travel around the channel faster than the particles are transported. Complementary to our experimental studies, a molecular dynamics simulation is used to extract local granular temperature and number density. It is found that the number density in the solid phase is several times that in the gas, while the temperature is orders of magnitude lower.

Figure 1

Geometry of the container and imaging system. Directions of basic vertical and rotational oscillations are indicated by arrows. For a description of the driving system see text.

Figure 2

Snapshots through the inner side wall of the channel covering 360° from experiment (left) and simulation (right) taken at $z(t)=0$ during the downwards motion of the container. Here the system sizes of simulation and experiment are equal. Time increases from top to bottom by 1.72 s (20 cycles) between consecutive snapshots. For clarity all images are stretched in the vertical direction by a factor of 4. ($f=11.6\mathrm{Hz}$, $\Gamma =1.23$.)

Figure 3

Solid fraction $L_s/L_0$ as a function of the peak container acceleration $\Gamma$ in experiment (filled circles) and simulation (open squares). Arrows indicate how the system evolves in the hysteresis loops. The inset is a space-time diagram of $\Delta n$ (see text for definition) from experiment for the parameters of Fig. 2. Solid regions appear dark.

Figure 4

Dimensionless velocity $v/(2\pi f{A}_v)$ of the phase boundaries as a function of the peak container acceleration $\Gamma$ in experiment (filled circles) and simulation (open circles). Open squares indicate the mean transport velocity obtained from numerical simulations.

Figure 5

Dimensionless temperature (top) and number density (bottom) from simulations with purely vertical forcing and $\Gamma =1.40$, $f=12.53\mathrm{Hz}$. The broken line in the lower graph indicates the average number density.