Scaling of convective velocity in a vertically vibrated granular bed

We experimentally study the velocity scaling of granular convection which is a possible mechanism of the regolith migration on the surface of small asteroids. In order to evaluate the contribution of granular convection to the regolith migration, the velocity of granular convection under the microgravity condition has to be revealed. Although it is hard to control the gravitational acceleration in laboratory experiments, scaling relations involving the gravitational effect can be evaluated by systematic experiments. Therefore, we perform such a systematic experiment of the vibration-induced granular convection. From the experimental data, a scaling form for the granular convective velocity is obtained. The obtained scaling form implies that the granular convective velocity can be decomposed into two characteristic velocity components: vibrational and gravitational velocities. In addition, the system size dependence is also scaled. According to the scaling form, the granular convective velocity $v$ depends on the gravitational acceleration $g$ as $v \propto g^{0.97}$ when the normalized vibrational acceleration is fixed.