Rotation and translation dynamics in a granular gas of rough spheres in microgravity
ORAL
Abstract
Granular gases are dilute ensembles of grains, interacting only in rare collision events, where energy is dissipated. Their collective dynamics have been studied analytically and numerically in numerous publications. One striking scenario is granular cooling, the decay of kinetic energy from an initially agitated state, originally modeled by P. Haff in1983 [1]. Experimental proof of the scaling laws was achieved only recently in 3D ensembles in microgravity [2,3]. It revealed striking quantitative disagreement with theory and previous simulations. One question concerns the role of particle rotations. For rods, rotaions around the short axis can be easily excited without friction, and those have been evaluated [2]. The purely frictionally or contact asymmetry excited rotation of spheres has previously not been addressed, for technical reasons. This is the
We present microgravity experiments using soft frictional spheres in a 3D setting. We analyze the role of translations and rotations during their granular cooling.
[1] P. K. Haff, Grain flow as a fluid-mechanical phenomenon, J. Fluid Mech. 134, 401 (1983).
[2] K. Harth, T. Trittel, S. Wegner, R. Stannarius, Phys. Rev. Lett. 120, 214301 (2018).
[3] P. Yu, M. Schröter, M. Sperl, Phys. Rev. Lett. 124, 208007 (2020).
We present microgravity experiments using soft frictional spheres in a 3D setting. We analyze the role of translations and rotations during their granular cooling.
[1] P. K. Haff, Grain flow as a fluid-mechanical phenomenon, J. Fluid Mech. 134, 401 (1983).
[2] K. Harth, T. Trittel, S. Wegner, R. Stannarius, Phys. Rev. Lett. 120, 214301 (2018).
[3] P. Yu, M. Schröter, M. Sperl, Phys. Rev. Lett. 124, 208007 (2020).
*We thank the German Aerospace Center (DLR) for funding within Grants 50WM2242 and 50WM2048, and for funding the drop tower time. We thank the team of ZARM Bremen for technical support. We thank ESA education for funding part of the drop tower experiments, and the members of the ESA Drop your Thesis! team Smart Dust (F. Guse, M. Zenker, P. Boße, A. Murath) for participation in the setup construction and providing some of the experimental data.
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Presenters
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Kirsten Harth
- Brandenburg University of Applied Science