Scaling relation for convective velocity in an intermittently vibrated granular packing

When a granular packing is mechanically vibrated in a container, convective motion of constituent particles (granular convection) is often induced. A scaling relation has been experimentally obtained for granular convective velocity under the steady vibration condition [Yamada & Katsuragi, Planet. Space Sci. 100, 79 (2014)]. However, the scaling relation for convective velocity in an intermittently vibrated granular packing has not been quantitatively obtained so far. In this study, we experimentally measured the granular convective motion in a two-dimensional granular packing under the successive intermittent tappings (each tapping event consists of a single period of sinusoidal oscillation). We calculated particle velocities using by the particle tracking velocimetry method. In addition, we investigated a vibration-condition dependence of convective velocity by systematically varying the amplitude and period of tappings. As a result, we found the scaling relation for convective velocity in an intermittently vibrated granular packing is almost identical to the scaling obtained with a steady vibration. Therefore, we conclude the intermittency of vibration doesn’t affect the velocity of granular convection.