Effects of initial conditions on the coalescence of micro-bubbles
Effects of initial conditions on the coalescence of micro-bubbles
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DOI：
10.1177/0954406217742941
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发表时间：
2018-02-01
影响因子：
2
通讯作者：
Zhu, Likun
中科院分区：
文献类型：
--
作者：
Chen, Rou;Yu, Huidan(Whitney);Zhu, Likun
采用格子Boltzmann方法研究了初始条件对水中两个等尺寸微气泡（R-0）合并的影响。重点是两个初始设置的母气泡，由一个小的距离d和连接的颈桥半径r（0），在早期阶段的气泡合并的颈桥生长的影响。一个复杂的自由能晶格玻尔兹曼方法模型的基础上Cahn-Hilliard扩散界面的方法。这种格子玻尔兹曼方法模型已被证明适用于处理高达1000的两种流体的大密度比，并能够最大限度地减少非物理寄生电流。在这两种初始情况下，颈桥的演变表现出半幂律缩放，r/R 0 =A0（t/ti）1/2后的发展时间。半幂律与最近的分析预测和实验结果一致。研究发现，较小的初始分离距离或较小的初始颈桥半径会导致颈桥的快速生长和气泡的聚并，这与这两种初始情况对液滴聚并的影响相似。每个行为背后的物理机制已经被探索。对于初始连接的情况，更快的颈部生长和更长的发展时间对应于较小的初始颈部半径是由于由弯月面曲率和颈部桥曲率贡献的毛细管力之间的显著偏差，而在初始分离的情况下，更快的生长和更短的发展时间对应于更短的分离距离是由于细长的颈部桥的形成。在每种情况下，代表颈桥半径在特征时间t（i）处增长的前因子A（0）与实验结果吻合良好。
The effects of initial conditions on the coalescence of two equal-sized air micro-bubbles (R-0) in water are studied using the lattice Boltzmann method. The focus is on effects of two initial set-ups of parent bubbles, separated by a small distance d and connected with a neck bridge radius r(0), on the neck bridge growth at the early stage of the bubble coalescence. A sophisticated free energy lattice Boltzmann method model based on the Cahn-Hilliard diffuse interface approach is employed. This lattice Boltzmann method model has been demonstrated suitable for handling a large density ratio of two fluids up to 1000 and capable of minimizing the nonphysical spurious current. In both initial scenarios, the neck bridge evolution exhibits a half power-law scaling, r/R0=A0(t/ti)1/2 after a development time. The half power-law agrees with the recent analytical prediction and experimental results. It has been found that smaller initial separation distance or smaller initial neck bridge radius results in faster growth of neck bridge and bubble coalescence, which is similar to the effects of these two initial scenarios on droplet coalescence. The physical mechanism behind each behavior has been explored. For the initial connected case, faster neck growth and longer development time corresponding to smaller initial neck radius is due to the significant bias between the capillary forces contributed by the meniscus curvature and the neck bridge curvature, whereas in the case of initial separated scenario, faster growth and shorter development time corresponding to shorter separation distance is due to the formation of elongated neck bridge. The prefactor A(0) that represents the growth of neck bridge radius at the characteristic time t(i) captured in each case is in good agreement with the experimental results.