混溶和不混溶环境中的旋转液滴动力学
Spinning drop dynamics in miscible and immiscible environments
摘要：
我们报告了旋转速度跃升后，可混溶和不混溶背景流体中旋转液滴的延伸动力学。观察到两种截然不同的行为。液滴在不混溶环境中以指数方式松弛到其平衡形状，松弛时间不依赖于离心力。我们发现一个很好的定量协议与预测的准球形滴石和布什（Q。54，551（1996）），而文献中提出的其他模型未能捕获我们的数据。相比之下，浸没在可混溶的背景流体中的液滴不会松弛成稳定形状：它们无限伸长，其长度遵循幂律$l(t)\sim t^{\frac{2}{5}}$，与Lister和Stone（J.Fluid Mech.317，275（1996））对非粘性液滴预测的动力学非常一致。我们的研究结果强烈表明，低的组成梯度在可混溶的流体不会引起一个有效的界面张力可测量的旋转滴张力法。
英文摘要：
We report on the extensional dynamics of spinning drops in miscible and immiscible background fluids following a rotation speed jump. Two radically different behaviours are observed. Drops in immiscible environments relax exponentially to their equilibrium shape, with a relaxation time that does not depend on the centrifugal forcing. We find an excellent quantitative agreement with the relaxation time predicted for quasi-spherical drops by Stone and Bush (Q. Appl. Math. 54, 551 (1996)), while other models proposed in the literature fail to capture our data. By contrast, drops immersed in a miscible background fluid do not relax to a steady shape: they elongate indefinitely, their length following a power-law $l(t)\sim t^{\frac{2}{5}}$ in very good agreement with the dynamics predicted by Lister and Stone (J. Fluid Mech. 317, 275 (1996)) for inviscid drops. Our results strongly suggest that low compositional gradients in miscible fluids do not give rise to an effective interfacial tension measurable by spinning drop tensiometry.
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