Granular Leidenfrost effect in microgravity

Abstract

When a container filled with granular material is subjected to vertical vibration in the presence of gravity, under certain conditions a non-monotonous density profile can be observed. This effect which is characteristic for dissipative granular gases, was termed “floating cluster regime” or “granular Leidenfrost effect”. Here, we study the behavior of vibro-agitated granular matter in the absence of gravity and identify a corresponding stationary state of the granulate, that is, we provide experimental evidence of the granular Leidenfrost effect under conditions of weightlessness.

Effect of the coefficient of restitution and friction in the granular Leidenfrost effect in the absence of gravity. A numerical study

“…The granular Leidenfrost effect is characterized by a a dilute region of fast moving particles supporting a region of dense particles. This effect has been demonstrated by under the effect of gravity [4], and recently demonstrated experimentally in the condition of microgravity [7]. Evidence of the granular Leidenfrost effect in the absence of gravity was demonstrated here by means of numerical simulations for the first time.…”

“…The numerical results greed qualitatively with measurements performed under microgravity. The experiments, as mentioned in [7], may have spurious gravity acceleration due to some imperfections in the parabolic flight which may have a large influence in the solid fraction distribution inside the vibrated container. Additionally, regions near the walls (below 0.5 and above 4.5 cm) may incorporate interference of the vibrating container's walls, which would generate artificially darken these regions and explain the larger packing fraction measured through Xray near the walls.…”

“…Nevertheless, this study inspired the authors at thinking on this experiment as a suitable to investigate material properties. With advances in X-ray tomography, similar experiments to the one proposed by [7] could be performed, e.g., in a drop tower [17], as an alternative to investigate elastic and frictional properties of granular materials, as the behavior seems to be quite sensitive to both.…”

“…Recently, [7] published the first experimental evidence of the existence of the granular Leidenfrost effect in microgravity, through experiments performed during a parabolic flight campaign. Reports of numerical studies of the aforementioned phenomena in the absence of gravity were not found by the authors.…”

“…* * e-mail: heiko.briesen@tum.de by [7]. The influence of the coefficient of restitution and the friction in the packing fraction of the granular media is investigated.…”