论文标题
粗糙泡沫中的多种动态状态
Multiple dynamic regimes in a coarsening foam
论文作者
论文摘要
我们使用差分动态显微镜和粒子跟踪来确定相互和直接空间中变形泡沫的动力学特性。在所有的WaveVectors $ Q $研究中，中间散射功能都表现出压缩的指数衰减。但是，访问前所未有的小$ q $ s强调了泡沫放松率$γ（q）$的$ q $依赖性的两个截然不同的政权。在任何给定的泡沫年龄，$γ（q）\ sim q $在高$ q $上，与方向存在和间歇性气泡位移一致。在低$ q $时，我们找到$γ（q）\ sim q^{1.6} $。我们表明，$ Q $第二级（Q）$的$ Q $依赖性的这种变化与气泡位移分布相关，表现出气泡直径的截止长度。对不同泡沫年龄的$γ$γ（Q）$的$ Q $依赖性的调查表明，泡沫动力学不仅受气泡长度尺度的控制，而且还受气泡生长所施加的应变率的控制。通过此应变率将$γ（Q）$归一化，而将$ q $乘以年龄依赖的气泡半径将所有数据集崩溃到唯一的主曲线上。
We use differential dynamic microscopy and particle tracking to determine the dynamical characteristics of a coarsening foam in reciprocal and direct space. At all wavevectors $q$ investigated, the intermediate scattering function exhibits a compressed exponential decay. However, the access to unprecedentedly small $q$s highlights the existence of two distinct regimes for the $q$-dependence of the foam relaxation rate $Γ(q)$. At any given foam age, $Γ(q)\sim q$ at high $q$, consistent with directionally-persistent and intermittent bubble displacements. At low $q$, we find $Γ(q) \sim q^{1.6}$. We show that such change in $q$-dependence of $Γ(q)$ relates to a bubble displacement distribution exhibiting a cut-off length of the order of the bubble diameter. Investigations of the $q$-dependence of $Γ(q)$ at different foam ages reveal that foam dynamics is not only governed by the bubble length scale, but also by the strain rate imposed by the bubble growth; normalizing $Γ(q)$ by this strain rate and multiplying $q$ with the age-dependent bubble radius leads to a collapse of all data sets onto a unique master-curve.
