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Shape deformation and oscillation of particle-laden bubbles after pinch-off from a nozzle
Chemical Engineering Journal ( IF 15.1 ) Pub Date : 2020-10-27 , DOI: 10.1016/j.cej.2020.127499
H. Wang , P.R. Brito-Parada

The rise of bubbles in liquid is a common phenomenon in chemical engineering applications. Bubble dynamics, however, are not fully understood, particularly at the early stages after bubbles are released from submerged nozzles, or when particles coat the bubble surface. In this work, a detailed investigation of microparticle-laden bubbles rising in water after being released from a nozzle was carried out to determine the influence of bubble surface coverage on the interface dynamics after pinch-off. The use of high-speed photography, at up to 25170 frames per second, allowed two regimes to be systematically investigated for the first time, i.e. an initial bubble shape deformation and shape oscillations. Surface pressure analysis shows that microparticles reduce the apparent surface tension of the interface by generating surface pressure during the initial bubble deformation. In contrast, during shape oscillations, little effect was observed on the period of the dominant harmonic, indicating that surface tension does not change during the oscillations. Harmonic analysis also showed that microparticles at bubble surfaces significantly increase the damping rate of the dominant harmonic, with a dependency on the bubble surface coverage. By quantifying the effect of particles on bubble dynamics, this work contributes to a better understanding of gas-liquid–solid reactors in which particle attachment plays a key role.



中文翻译:

从喷嘴夹断后,载有气泡的气泡的形状变形和振荡

液体中气泡的上升是化学工程应用中的常见现象。然而,气泡动力学还没有被完全理解,特别是在气泡从浸没式喷嘴释放后的早期,或者当颗粒覆盖气泡表面时。在这项工作中,对从喷嘴释放后在水中上升的载有微粒的气泡进行了详细研究,以确定气泡表面覆盖对夹断后界面动力学的影响。每秒高达25170帧的高速摄影的使用,使得首次可以对两种状态进行系统地研究,即初始气泡形状变形和形状振荡。表面压力分析表明,微粒通过在初始气泡变形过程中产生表面压力来降低界面的表观表面张力。相反,在形状振荡期间,几乎没有观察到主导谐波的周期,这表明在振荡期间表面张力没有变化。谐波分析还显示,气泡表面的微粒会显着提高主导谐波的阻尼率,这取决于气泡表面的覆盖率。通过量化颗粒对气泡动力学的影响,这项工作有助于更好地理解其中颗粒附着起关键作用的气液固反应器。表示在振荡过程中表面张力不会改变。谐波分析还显示,气泡表面的微粒会显着提高主导谐波的阻尼率,这取决于气泡表面的覆盖率。通过量化颗粒对气泡动力学的影响,这项工作有助于更好地理解其中颗粒附着起关键作用的气液固反应器。表示在振荡过程中表面张力不会改变。谐波分析还显示,气泡表面的微粒会显着提高主导谐波的阻尼率,这取决于气泡表面的覆盖率。通过量化颗粒对气泡动力学的影响,这项工作有助于更好地理解其中颗粒附着起关键作用的气液固反应器。

更新日期:2020-10-30
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