Stable small bubble clusters in two-dimensional foams.
Stable small bubble clusters in two-dimensional foams.
复制标题
二维泡沫中稳定的小气泡簇。
DOI：
10.1039/c7sm00723j
复制
发表时间：
2017
期刊：
影响因子：
3.4
通讯作者：
M. Dennin
中科院分区：
文献类型：
--
作者：
Kai Zhang;Chin;N. See;C. O’Hern;M. Dennin
无定形颗粒材料，如泡沫，乳液和粒状介质，施加应力的机械响应的关键特征是由系统从一个机械稳定状态过渡到另一个时发生的颗粒重排的频率和尺寸决定的。这项工作描述了协调的实验和计算研究的气泡筏，这是准二维系统的气泡局限于空气-水界面。我们专注于小的机械稳定的四，五，六，七个气泡与两种不同的尺寸与直径比σL/σS <$1.4的集群。专注于小气泡集群，这可以被看作是一个更大的系统的子系统，使我们能够调查的完整合奏的集群的形式，测量各自的频率与集群发生，并确定形式的气泡相互作用。我们强调几个重要的结果。首先，对于具有N > 5个气泡的团簇，我们发现使用离散元模拟，与由长程吸引相互作用产生的团簇相比，气泡之间的短程吸引相互作用产生更大的不同机械稳定的团簇系综。在具有短程吸引力的系统中，额外的集群在集群外围的相邻气泡对之间具有更大的间隙。实验中观察到的气泡团簇系综与长程吸引相互作用的团簇系综相似。我们还比较了每个集群在模拟和实验中发生的频率。我们发现，集群频率是非常敏感的协议，用于产生它们，只有弱相关的集群的能量。
Key features of the mechanical response of amorphous particulate materials, such as foams, emulsions, and granular media, to applied stress are determined by the frequency and size of particle rearrangements that occur as the system transitions from one mechanically stable state to another. This work describes coordinated experimental and computational studies of bubble rafts, which are quasi-two dimensional systems of bubbles confined to the air-water interface. We focus on small mechanically stable clusters of four, five, six, and seven bubbles with two different sizes with diameter ratio σL/σS ≃ 1.4. Focusing on small bubble clusters, which can be viewed as subsystems of a larger system, allows us to investigate the full ensemble of clusters that form, measure the respective frequencies with which the clusters occur, and determine the form of the bubble-bubble interactions. We emphasize several important results. First, for clusters with N > 5 bubbles, we find using discrete element simulations that short-range attractive interactions between bubbles give rise to a larger ensemble of distinct mechanically stable clusters compared to that generated by long-range attractive interactions. The additional clusters in systems with short-range attractions possess larger gaps between pairs of neighboring bubbles on the periphery of the clusters. The ensemble of bubble clusters observed in experiments is similar to the ensemble of clusters with long-range attractive interactions. We also compare the frequency with which each cluster occurs in simulations and experiments. We find that the cluster frequencies are extremely sensitive to the protocol used to generate them and only weakly correlated to the energy of the clusters.