Microbubble formation and pinch-off scaling exponent in flow-focusing devices
Microbubble formation and pinch-off scaling exponent in flow-focusing devices
复制标题
DOI：
10.1063/1.3631323
复制
发表时间：
2011-02
影响因子：
4.6
通讯作者：
W. V. Hoeve;B. Dollet;M. Versluis;D. Lohse
中科院分区：
文献类型：
--
作者：
W. V. Hoeve;B. Dollet;M. Versluis;D. Lohse
在最近的实验中，我们使用1×106帧/S的超高速成像技术研究了微流控流动聚焦装置中气体射流的破裂和由此产生的微气泡的形成。莱特牧师。034504(2008年)]，发现在崩塌的最后阶段，颈部半径与时间成1/3的幂指数关系，这表明气体惯性和伯努利吸力效应是重要的。在这里，超高速成像被用来捕捉完整的气泡轮廓并量化通过颈部的气体流动。高时间分辨率的图像使我们能够接近夹断的最后时刻，在1μ以内，S，它揭示了在崩塌过程中，气体流动逆转，并加速到夹断时刻的最大速度。然而，由于伯努利吸力导致的压力下降太低，无法解释加速坍塌的原因。我们观察到崩溃过程的两个阶段。首先，颈缩缩的标度指数为1/3，这可以用“填充效应”来解释。在最后阶段，崩塌的特征是标度指数为2/5，根据观察到在崩塌过程中，由于穿过液体的惯性，颈部变得不那么细长，可以推导出标度指数。然而，直到夹断前的最后一微秒，表面张力仍然是重要的。
We investigate the gas jet breakup and the resulting microbubble formation in a microfluidic flow-focusing device using ultra high-speed imaging at 1 × 106 frames/s. In recent experiments [Dollet et al., Phys. Rev. Lett. 100, 034504 (2008)], it was found that in the final stage of the collapse the radius of the neck scales with time with a 1/3 power-law exponent, which suggested that gas inertia and the Bernoulli suction effect become important. Here, ultra high-speed imaging was used to capture the complete bubble contour and quantify the gas flow through the neck. The high temporal resolution images enable us to approach the final moment of pinch-off to within 1 μs. It revealed that during the collapse, the flow of gas reverses and accelerates towards its maximum velocity at the moment of pinch-off. However, the resulting decrease in pressure, due to Bernoulli suction, is too low to account for the accelerated collapse. We observe two stages of the collapse process. At first, the neck collapses with a scaling exponent of 1/3 which is explained by a “filling effect.” In the final stage, the collapse is characterized by a scaling exponent of 2/5, which can be derived, based on the observation that during the collapse the neck becomes less slender, due to the driving through liquid inertia. However, surface tension forces are still important until the final microsecond before pinch-off