Thermal expansion effects and heat conduction in granular materials.

ABSTRACT

In this paper, we report results and analysis on a simulation study of the effects of thermal expansion in granular systems. We show that these effects impact the force distribution inside a two-dimensional system of disks that are subject to thermal heating under two different boundary conditions. A significant increase in the average force is observed for steel particles confined within a box with fixed walls at temperature rises of 50 degrees C and 100 degrees C, respectively. As previously noted in the literature, thermal expansion also induces compaction. The results show that a systematic and controllable increase in granular packing can be induced by simply raising and then lowering the temperature, without the input of mechanical energy in agreement with previous experimental observations. We find that the evolution of the packing fraction is well described by a fractional relaxation model, which follows the Mittag-Leffler law.