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arXiv 0908.1592cond-mat.softcond-mat.stat-mech
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无序盘中受驱动探针粒子的涨落、干扰和屈服

Fluctuations, Jamming, and Yielding for a Driven Probe Particle in Disordered Disk Assemblies

C. J. Olson Reichhardt, C. Reichhardt

摘要:

使用数值模拟,我们研究的速度波动的探针粒子驱动的恒定的力通过一个二维的无序组装的磁盘,其中有一个明确的干扰点J的密度为0.843。随着λ向λ_J方向增加,探测粒子的平均速度减小,速度波动表现出越来越多的间歇性或雪崩状行为。当系统距离干扰密度小于百分之几时,速度分布为指数分布;当系统距离干扰密度小于百分之一时,速度分布为非指数或幂律分布。速度功率谱在干扰附近表现出从洛伦兹形式到1/f形状的交叉。我们提取的相关指数ν是在最近的剪切模拟很好的协议。当λ> λ_J时,存在一个临界阈值力F_c,该临界力F_c随λ_J的增大而增大。探针运动的起始点在π_J以上,通过探针粒子周围的粒子的局部屈服发生,我们称之为局部剪切带效应。

英文摘要:

Using numerical simulations we examine the velocity fluctuations of a probe particle driven with constant force through a two-dimensional disordered assembly of disks which has a well-defined jamming point J at a density of ϕ_J=0.843. As ϕincreases toward ϕ_J, the average velocity of the probe particle decreases and the velocity fluctuations show an increasingly intermittent or avalanchelike behavior. When the system is within a few percent of the jamming density, the velocity distributions are exponential, while when the system is less than a percent away from jamming, the velocity distributions have a non-exponential or power law character. The velocity power spectra exhibit a crossover from a Lorentzian form to a 1/f shape near jamming. We extract a correlation exponent νwhich is in good agreement with recent shear simulations. For ϕ> ϕ_J, there is a critical threshold force F_c that must be applied for the probe particle to move through the sample which increases with increasing ϕ. The onset of the probe motion above ϕ_J occurs via a local yielding of the particles around the probe particle which we term a local shear banding effect.

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