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The dynamics of compound drops at high Reynolds numbers: Drag, shape, and trajectory
International Journal of Multiphase Flow ( IF 3.6 ) Pub Date : 2021-05-26 , DOI: 10.1016/j.ijmultiphaseflow.2021.103699
Joel R. Karp , Ernesto Mancilla , Fabricio S. da Silva , Dominique Legendre , Roberto Zenit , Rigoberto E.M. Morales

The behaviour of compound drops rising at high Reynolds numbers, roughly 60 to 700, was studied experimentally for a wide range of diameter ratios and three different combinations of the internal and external fluids. Two rising regimes were identified, namely a rectilinear and an oscillatory trajectory. The governing effects in each motion regime were discussed. The compound drops presented mild shape distortions in all the measurements, suggesting that the internal fluid movement might play an essential role in the motion transition. The compound drops presented a stable path when the internal bubble is small with viscous effects governing the motion. The internal bubble reduced the viscous dissipation and the drag coefficient exhibited intermediate values compared to correspondent single-fluid drops and bubbles. For a large internal bubble, the path of the compound drops becomes oscillatory and viscous effects are diminished. The oscillation is characterized by a relative motion of the external fluid relative to the inner bubble, thus increasing the drag coefficient. Mechanistic models for the drag coefficient based on the governing dimensionless numbers of the flow were proposed, and they showed a good agreement with the measurements.



中文翻译:

高雷诺数下复合液滴的动力学:阻力、形状和轨迹

化合物液滴在高雷诺数(大约 60 到 700)下上升的行为通过实验研究了各种直径比和三种不同的内部和外部流体组合。确定了两种上升状态,即直线和振荡轨迹。讨论了每种运动方式的控制效应。复合液滴在所有测量中都呈现出轻微的形状扭曲,表明内部流体运动可能在运动过渡中起重要作用。当内部气泡较小时,复合液滴呈现出稳定的路径,粘性效应控制着运动。与相应的单流体液滴和气泡相比,内部气泡减少了粘性耗散,阻力系数呈现中间值。对于较大的内部气泡,复合液滴的路径变得振荡,粘性效应减弱。振荡的特点是外部流体相对于内部气泡的相对运动,从而增加了阻力系数。提出了基于流动的控制无量纲数的阻力系数的力学模型,它们与测量结果非常吻合。

更新日期:2021-06-05
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