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Bubble fragmentation dynamics in a subsonic Venturi tube for the design of a compact microbubble generator
International Journal of Multiphase Flow ( IF 3.8 ) Pub Date : 2021-03-25 , DOI: 10.1016/j.ijmultiphaseflow.2021.103645
Yuichi Murai , Yuji Tasaka , Yoshihiko Oishi , Patricia Ern

Microbubble generators are in wide demand in industry following the discovery of a number of new functions of microbubble mixtures. This paper deals with a Venturi tube microbubble generator in which air bubbles at the inlet are fragmented in the diverging part of the tube. In contrast with past studies, we here regulated the flow subsonic so that fragmentation occurred without the help of pressure shock waves. Counting the microbubbles in image processing, we found that a single bubble fragmented into 20–400 microbubbles depending on the Weber number. The power efficiency is found to range from 30 to 50 percent and insensitive to the liquid viscosity. The mechanism of subsonic fragmentation is elucidated adopting particle tracking velocimetry, in association with a theoretical description of the translational motion and the shape oscillation of the bubble. The key event was found to be the bubble's rapid slip-back in the diverging part of the Venturi tube due to a positive pressure gradient. This provides a function that prevents large bubbles from being released from the subsonic Venturi tube.



中文翻译:

设计紧凑型微气泡发生器的亚音速文丘里管中的气泡破碎动力学

随着微泡混合物的许多新功能的发现,微泡发生器在工业中得到了广泛的需求。本文介绍了一种文丘里管微气泡发生器,其中入口处的气泡在管的发散部分被破碎。与以往的研究相反,我们在此调节亚音速流,从而在没有压力冲击波的情况下发生碎裂。计数图像处理中的微气泡,我们发现一个气泡根据Weber数分为20–400个微气泡。发现功率效率为30%至50%,并且对液体粘度不敏感。利用粒子跟踪测速技术阐明了亚音速破碎的机理,结合对平移运动和气泡形状振荡的理论描述。发现关键事件是由于正压力梯度,在文丘里管的发散部分中气泡的快速回滑。这提供了防止大气泡从亚音速文丘里管释放的功能。

更新日期:2021-04-01
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