arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1502.01235cond-mat.stat-mechcond-mat.soft
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颗粒系统中的粗化

Coarsening in granular systems

Andrea Baldassarri, Andrea Puglisi, Alessandro Sarracino

摘要:

我们回顾了一些有代表性的例子,颗粒实验或模型相分离,伴随着域粗化,是一个相关的现象。我们首先阐明了内在的非平衡,或非热,颗粒介质的性质。此后,稀释系统,所谓的“粒状气体”进行了讨论:理想化的动力学模型,如在冷却制度的非弹性硬球的气体,是最佳的游乐场,以研究相关的结构,如剪切模式,涡和集群的缓慢增长。在流化实验中,已经观察到液-气或固-气分离。在单层颗粒的情况下,相共存和粗化出现在几个不同的设置,与机械或静电能量输入。唯象模型描述,甚至定量,几个实验措施,无论是粗化动力学和不同的颗粒相之间的动态过渡。基本的双稳态的起源一般与颗粒流体力学计算的负压缩性有关,即使对该机制的理解还远未完成。在重要的工业应用中,一个相关的问题涉及混合物的分层或分离,例如在旋转的滚筒中或在水平振动的板上。最后,具有许多重要应用的高密度颗粒材料的压实问题通常用粗化动力学来描述:在那里,未对准的颗粒的气泡蒸发,允许最佳排列的岛的合并和总占用体积的逐渐减少。

英文摘要:

We review a few representative examples of granular experiments or models where phase separation, accompanied by domain coarsening, is a relevant phenomenon. We first elucidate the intrinsic non-equilibrium, or athermal, nature of granular media. Thereafter, dilute systems, the so-called "granular gases" are discussed: idealized kinetic models, such as the gas of inelastic hard spheres in the cooling regime, are the optimal playground to study the slow growth of correlated structures, e.g. shear patterns, vortices and clusters. In fluidized experiments, liquid-gas or solid-gas separations have been observed. In the case of monolayers of particles, phase coexistence and coarsening appear in several different setups, with mechanical or electrostatic energy input. Phenomenological models describe, even quantitatively, several experimental measures, both for the coarsening dynamics and for the dynamic transition between different granular phases. The origin of the underlying bistability is in general related to negative compressibility from granular hydrodynamics computations, even if the understanding of the mechanism is far from complete. A relevant problem, with important industrial applications, is related to the demixing or segregation of mixtures, for instance in rotating tumblers or on horizontally vibrated plates. Finally, the problem of compaction of highly dense granular materials, which has many important applications, is usually described in terms of coarsening dynamics: there, bubbles of mis-aligned grains evaporate, allowing the coalescence of optimally arranged islands and a progressive reduction of total occupied volume.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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