The effect of surfactants on the tail and film dynamics of elongated gas bubbles propagating through circular capillary tubes is investigated by means of an extensive three-dimensional numerical study using a hybrid front-tracking/level-set method. The focus is on the visco-inertial regime, which occurs when the Reynolds number of the flow is much larger than unity. Under these conditions, clean' bubbles exhibit interface undulations in the proximity of the tail \cite{Magnini_prf_2017}, with an amplitude that increases with the Reynolds number. We perform a systematic analysis of the impact of a wide range of surfactant properties, including elasticity, bulk surfactant concentration, solubility, and diffusivity, on the bubble and flow dynamics in the presence of inertial effects. The results show that the introduction of surfactants is effective in suppressing the tail undulations as they tend to accumulate near the bubble tail. Here, large Marangoni stresses are generated, which lead to a localrigidification’ of the bubble. This effect becomes more pronounced for larger surfactant elasticities and adsorption depths. At reduced surfactant solubility, a thicker rigid film region forms at the bubble rear, where a Couette film flow is established, while undulations still appear at the trailing edge of the downstream `clean’ film region. In such conditions, the bubble length becomes an influential parameter, with short bubbles becoming completely rigid.

中文翻译：

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表面活性剂对高雷诺数毛细管中拉长气泡的影响

表面活性剂对通过圆形毛细管传播的细长气泡的尾部和薄膜动力学的影响是通过广泛的三维数值研究方法进行研究的，其中使用了混合前跟踪/水平集方法。重点是粘惯性状态，当流的雷诺数远大于一时会发生。在这种情况下clean' bubbles exhibit interface undulations in the proximity of the tail \cite{Magnini_prf_2017}, with an amplitude that increases with the Reynolds number. We perform a systematic analysis of the impact of a wide range of surfactant properties, including elasticity, bulk surfactant concentration, solubility, and diffusivity, on the bubble and flow dynamics in the presence of inertial effects. The results show that the introduction of surfactants is effective in suppressing the tail undulations as they tend to accumulate near the bubble tail. Here, large Marangoni stresses are generated, which lead to a local泡沫的僵化”。对于较大的表面活性剂弹性和吸附深度，该效果变得更加明显。在降低表面活性剂溶解度的情况下，在气泡后部会形成较厚的硬膜区域，在此处形成库埃特膜流动，而在下游“清洁”膜区域的后缘仍会出现起伏。在这种情况下，气泡长度成为影响参数，而短气泡则变得完全刚性。