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arXiv 1706.07541physics.flu-dyn
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液滴冲击固体表面的动力学:冲击力的演化和自相似扩展

Dynamics of drop impact on solid surfaces: evolution of impact force and self-similar spreading

Leonardo Gordillo, Ting-Pi Sun, Xiang Cheng

摘要:

我们调查的动态下降的影响干燥固体表面。通过同步高速摄影与快速力传感,我们同时测量的时间演变的形状和冲击力的影响下降了很大范围的雷诺数(Re)。在高Re,当惯性占主导地位的影响过程中,我们表明,早期的冲击力的演变遵循平方根标度,定量同意最近的自相似理论。这一观测结果提供了直接的实验证据的存在向上传播的自相似压力场的初始冲击液滴在高Re。当粘性力随着Re的减小而逐渐增加时,我们用摄动法分析了粘性液滴冲击力的早期标度。分析定量匹配我们的实验,并成功地预测了最大冲击力的趋势和相关的峰值时间与减少Re。此外,我们讨论了粘弹性的影响的时间签名的冲击力。最后但并非最不重要的是,我们还研究了在高Re的液滴的扩展后的初始冲击。特别是,我们找到了一个精确的参数自由自相似的解决方案,惯性驱动的液滴扩展,定量预测的高度扩展滴在高Re。文中还讨论了液滴扩散自相似方法的局限性。因此,我们的研究提供了一个定量的理解的时间演变的冲击力的惯性,粘性和粘弹性制度,并揭示了新的光下降冲击过程的自相似动力学。

英文摘要:

We investigate the dynamics of drop impacts on dry solid surfaces. By synchronising high-speed photography with fast force sensing, we simultaneously measure the temporal evolution of the shape and impact force of impacting drops over a wide range of Reynolds numbers (Re). At high Re, when inertia dominates the impact processes, we show that the early-time evolution of impact force follows a square-root scaling, quantitatively agreeing with a recent self-similar theory. This observation provides direct experimental evidence on the existence of upward propagating self-similar pressure fields during the initial impact of liquid drops at high Re. When viscous forces gradually set in with decreasing Re, we analyse the early-time scaling of the impact force of viscous drops using a perturbation method. The analysis quantitatively matches our experiments and successfully predicts the trends of the maximum impact force and the associated peak time with decreasing Re. Furthermore, we discuss the influence of viscoelasticity on the temporal signature of impact forces. Last but not least, we also investigate the spreading of liquid drops at high Re following the initial impact. Particularly, we find an exact parameter-free self-similar solution for the inertia-driven drop spreading, which quantitatively predicts the height of spreading drops at high Re. The limit of the self-similar approach for drop spreading is also discussed. As such, our study provides a quantitative understanding of the temporal evolution of impact forces across the inertial, viscous and viscoelastic regimes and sheds new light on the self-similar dynamics of drop impact processes.

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