Brownian motion in shear flow: Direct observation of anomalous diffusion
Brownian motion in shear flow: Direct observation of anomalous diffusion
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DOI：
10.1103/physreve.84.061120
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发表时间：
2011-12-12
影响因子：
2.4
通讯作者：
Takikawa, Yoshinori
中科院分区：
文献类型：
--
作者：
Orihara, Hiroshi;Takikawa, Yoshinori
本文用不同的观察和分析方法对简单剪切流中的布朗运动进行了实验研究。用激光共聚焦扫描显微镜对分散在剪切水中的聚苯乙烯微球进行了跟踪，得到了微球坐标随时间的变化规律。由于在通常的均方位移在流动方向上的布朗运动的贡献是压倒了由于对流，我们认为一个替代的位移对流效应可以被删除。我们发现，新的均方位移由正常的爱因斯坦扩散项和反常的t（3）项组成，前者与t成线性关系，后者是由沿着速度梯度的扩散与对流之间的耦合引起的。
Brownian motion in a simple shear flow has been experimentally investigated by using a different method for observation and analysis. A number of polystyrene spheres dispersed in sheared water were tracked with a confocal scanning laser microscope, and the time dependences of their coordinates were obtained. Since in the usual mean-square displacement in the flow direction the contribution from the Brownian motion is overwhelmed by that due to the convection, we considered an alternative displacement for which the convection effect could be removed. We found that the new mean-square displacement consists of the normal Einstein diffusion term, which is linear in t, and an anomalous t(3) term arising from the coupling between the diffusion along the velocity gradient and the convection.