Simultaneous measurements of deforming Hinze-scale bubbles with surrounding turbulence
Simultaneous measurements of deforming Hinze-scale bubbles with surrounding turbulence
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DOI：
10.1017/jfm.2020.933
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发表时间：
2021-01
影响因子：
3.7
通讯作者：
A. U. M. Masuk;Ashwanth K. R. Salibindla;R. Ni
中科院分区：
文献类型：
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作者：
A. U. M. Masuk;Ashwanth K. R. Salibindla;R. Ni
摘要对Hinze尺度气泡在湍流中的破碎机理和破碎概率进行了实验研究。Hinze尺度被定义为基于临界平均韦伯数的临界气泡尺寸，在该临界平均韦伯数上，气泡破裂概率被认为具有从由湍流应力主导到由表面张力完全抑制的突然转变。在这项工作中，量化的破碎概率的大小接近Hinze尺度的气泡，并检查不同的破碎机制，气泡和它们周围的示踪粒子同时跟踪。从实验结果中，两个韦伯数，一个从两个阶段之间的滑移速度计算，另一个从当地的速度梯度，分离和拟合的模型，可以链接回湍流特性。此外，我们还提供了一个经验模型连接气泡变形的两个韦伯数通过扩展的关系从势流理论。气泡的长宽比和韦伯数之间的建议的关系，似乎一直很好的工作范围内的气泡尺寸。利用线性受迫振子模型将气泡长径比和两个韦伯数的时间轨迹联系起来。最后，获得这两个韦伯数的分布提供了一种独特的方式来提取破碎概率的大小接近Hinze尺度的气泡。
Abstract We experimentally investigate the breakup mechanisms and probability of Hinze-scale bubbles in turbulence. The Hinze scale is defined as the critical bubble size based on the critical mean Weber number, across which the bubble breakup probability was believed to have an abrupt transition from being dominated by turbulence stresses to being suppressed completely by the surface tension. In this work, to quantify the breakup probability of bubbles with sizes close to the Hinze scale and to examine different breakup mechanisms, both bubbles and their surrounding tracer particles were simultaneously tracked. From the experimental results, two Weber numbers, one calculated from the slip velocity between the two phases and the other acquired from local velocity gradients, are separated and fitted with models that can be linked back to turbulence characteristics. Moreover, we also provide an empirical model to link bubble deformation to the two Weber numbers by extending the relationship obtained from potential flow theory. The proposed relationship between bubble aspect ratio and the Weber numbers seems to work consistently well for a range of bubble sizes. Furthermore, the time traces of bubble aspect ratio and the two Weber numbers are connected using the linear forced oscillator model. Finally, having access to the distributions of these two Weber numbers provides a unique way to extract the breakup probability of bubbles with sizes close to the Hinze scale.