# Gravity flows

## F. Vivanco, F. Melo

We study experimentally as well as a numerically two-dimensional gravity flows. The influence of dynamical arches on time behavior of this system reveals a strong correlation between dynamical arches and the time fluctuations of the average vertical velocity. Our numerical simulation is based on the contact dynamic method and accounts well for the experimental finding. Recently, we have completed this study by including a theoretical approach based on a simple purely kinematic model for the grains motion. In addition, by generalizing the well known "Hourglass Theory", we have developed a simple model capturing the main features of the flow.

Figure 1. Snapshots of force distribution during the flow in a two dimensional hourglass.

Figure 2. (a) Spatial average of vertical velocity and total length of force chains vs normalized time. (b) Correlation of spatial average of vertical velocity and total length of force chains. (c) Correlation of spatial average of vertical acceleration and total length of force chains.

Figure 3. Mass outflow rate per unit of angle and density at the aperture.