Fig. 4
Schematic drawing of the different evolution of fluidized granular media with increasing the filling fraction Φ on the ground (g) and in microgravity (μg) based on the DWS measurements. The samples become fully fluidized in both cases at low-filling fraction. The sample stays settled with moderate packing fraction and a free surface on the ground (intermediate green area), while it expands in microgravity to fill the cell with a low packing fraction (light green area). This gives space for the formation and motion of larger voids in the sample than on the ground (white areas). An increase of Φ close to the limit of full arrest leads to a homogeneous fluidized state with high packing fraction in microgravity (dark green area). On the ground, the sample separates into steady fluidized regions where the packing fraction of the fully fluidized state is locally preserved (intermediate green areas), and into arrested densely packed regions (red area). Further increase in packing fraction leads to fully arrested samples in both cases (red area, ΔΦ = 0)
