Adachi Masato, Yu Peidong, Sperl Matthias
1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt (DLR), 51170 Köln, Germany.
2Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany.
NPJ Microgravity. 2019 Aug 13;5:19. doi: 10.1038/s41526-019-0079-y. eCollection 2019.
A thermostat utilizing a varying magnetic field has been developed to agitate soft ferromagnetic particles in microgravity platforms for an investigation of an energy-dissipative granular gas. Although the method has experimentally realized a reasonably homogeneous spatial distribution of particles, the physics behind the magnetically excited particles has not been understood. Therefore, a numerical calculation based on the discrete element method is developed in this paper to explain the realization of homogeneously distributed particles. The calculation method allows considering inelastic and magnetic interactions between particles and tracking the motions due to those interactions during the excitation of the granular gas. The calculation results, compared with the experimental result, show that magnetic interactions between particles, a time-domain variation of magnetic-excitation directions, and random collisions of particles between each magnetic excitation contribute to distribute particles homogeneously.
一种利用变化磁场的恒温器已被开发出来，用于在微重力平台中搅动软铁磁颗粒，以研究能量耗散的颗粒气体。尽管该方法已通过实验实现了颗粒相当均匀的空间分布，但磁激发颗粒背后的物理原理尚未被理解。因此，本文开发了一种基于离散元法的数值计算方法来解释颗粒均匀分布的实现过程。该计算方法能够考虑颗粒之间的非弹性和磁性相互作用，并跟踪颗粒气体激发过程中由于这些相互作用而产生的运动。计算结果与实验结果相比表明，颗粒之间的磁性相互作用、磁激发方向的时域变化以及每次磁激发之间颗粒的随机碰撞有助于使颗粒均匀分布。
