Université Paris Cité, CNRS, MSC, UMR 7057, F-75013 Paris, France.
Phys Rev E. 2023 Mar;107(3-1):034903. doi: 10.1103/PhysRevE.107.034903.
We present an experimental study of the dynamics of a set of magnets within a fluid in which a remote torque applied by a vertical oscillating magnetic field transfers angular momentum to individual magnets. This system differs from previous experimental studies of granular gas where the energy is injected by vibrating the boundaries. Here, we do not observe any cluster formation, orientational correlation and equipartition of the energy. The magnets' linear velocity distributions are stretched exponentials, similar to three-dimensional boundary-forced dry granular gas systems, but the exponent does not depend on the number of magnets. The value of the exponent of the stretched exponential distributions is close to the value of 3/2 previously derived theoretically. Our results also show that the conversion rate of angular momentum into linear momentum during the collisions controls the dynamics of this homogenously forced granular gas. We report the differences among this homogeneously forced granular gas, ideal gas, and nonequilibrium boundary-forced dissipative granular gas.
我们进行了一项关于一组磁铁在流体中动力学的实验研究，在该实验中，通过垂直振荡磁场施加的远程扭矩将角动量传递给单个磁铁。与先前通过振动边界注入能量的颗粒气体的实验研究不同，在这里，我们没有观察到任何团簇形成、取向相关和能量的均分。磁铁的线性速度分布呈拉伸指数形式，类似于三维边界强制干燥颗粒气体系统，但指数并不取决于磁铁的数量。拉伸指数分布的指数值接近先前从理论上推导出来的 3/2 值。我们的结果还表明，在碰撞过程中角动量向线性动量的转换速率控制着这种均匀强制颗粒气体的动力学。我们报告了这种均匀强制颗粒气体、理想气体和非平衡边界强制耗散颗粒气体之间的差异。
