论文标题
在强限制下的非弹性标记粒子的动力学
Dynamics of an inelastic tagged particle under strong confinement
论文作者
论文摘要
浸入相同大小的颗粒流体中的标记粒子的动力学，但是当系统限制在两个硬平行板之间时，研究了不同的质量，分隔了小于颗粒直径的两倍的距离。颗粒之间的碰撞是无弹性的，而粒子与硬壁的碰撞在垂直于壁的方向上注入能量，因此可以在长期限制下达到固定状态。标记粒子的速度分布验证了一个玻尔兹曼 - 洛伦兹式方程，该方程是假设它是一种具有两个不同温度的空间均匀的高斯分布（一个与壁平行的运动有关，另一个与垂直方向相关）。发现当标记的粒子质量从下方接近临界质量时，垂直于壁的温度散开，而平行温度保持有限。分子动力学仿真结果与临界质量以下标记的粒子质量的理论预测非常吻合。标记粒子的速度分布函数的测量值证实，如果质量不接近临界质量，则是高斯，而在接近临界质量时，它会偏离高斯。在临界质量上方，速度分布函数远离高斯，是垂直方向的边缘分布，差异比平行方向的差异要大得多。
The dynamics of a tagged particle immersed in a fluid of particles of the same size but different mass is studied when the system is confined between two hard parallel plates separated a distance smaller than twice the diameter of the particles. The collisions between particles are inelastic while the collisions of the particles with the hard walls inject energy in the direction perpendicular to the wall, so that stationary states can be reached in the long-time limit. The velocity distribution of the tagged particle verifies a Boltzmann-Lorentz-like equation that is solved assuming that it is a spatially homogeneous gaussian distribution with two different temperatures (one associated to the motion parallel to the wall and another associated to the perpendicular direction). It is found that the temperature perpendicular to the wall diverges when the tagged particle mass approaches a critical mass from below, while the parallel temperature remains finite. Molecular Dynamics simulation results agree very well with the theoretical predictions for tagged particle masses below the critical mass. The measurements of the velocity distribution function of the tagged particle confirm that it is gaussian if the mass is not close to the critical mass, while it deviates from gaussianity when approaching the critical mass. Above the critical mass, the velocity distribution function is very far from a gaussian, being the marginal distribution in the perpendicular direction bimodal and with a much larger variance than the one in the parallel direction.
