Capillary-scale solid rebounds: experiments, modelling and simulations
Capillary-scale solid rebounds: experiments, modelling and simulations
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DOI：
10.1017/jfm.2020.1135
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发表时间：
2020-10
影响因子：
3.7
通讯作者：
Carlos A. Galeano-Rios;R. Cimpeanu;Isabelle A. Bauman;Annika MacEwen;P. Milewski;D. Harris
中科院分区：
文献类型：
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作者：
Carlos A. Galeano-Rios;R. Cimpeanu;Isabelle A. Bauman;Annika MacEwen;P. Milewski;D. Harris
摘要 撞击静止浴自由表面的毫米级超疏水球体可以通过毛细管效应和动态流体力被推回到空气中，同时将其部分能量传递给流体。我们报告了对这一现象进行彻底调查的结果，涉及不同的方法。从产生反弹所需的最小冲击速度到导致固体球下沉的冲击速度，我们重点关注恢复系数、接触时间和最大表面偏转对问题的不同物理参数的依赖性。实验、模拟和渐近分析揭示了反弹指标的趋势，揭示了韦伯数谱两端的新现象，并折叠了数据。使用伪实心球的直接数值模拟成功地再现了实验数据，同时还提供了对难以通过实验确定的流量的深入了解。基于将完全疏水的冲击器的运动与线性化的无流体表面相匹配的模型通过直接数值模拟进行了验证，并在低韦伯数状态下使用。本研究中的分层和交叉验证模型使我们能够在具有挑战性的多尺度系统中探索整个目标参数空间。
Abstract A millimetre-size superhydrophobic sphere impacting on the free surface of a quiescent bath can be propelled back into the air by capillary effects and dynamic fluid forces, whilst transferring part of its energy to the fluid. We report the findings of a thorough investigation of this phenomenon, involving different approaches. Over the range from minimum impact velocities required to produce rebounds to impact velocities that cause the sinking of the solid sphere, we focus on the dependence of the coefficient of restitution, contact time and maximum surface deflection on the different physical parameters of the problem. Experiments, simulations and asymptotic analysis reveal trends in the rebound metrics, uncover new phenomena at both ends of the Weber number spectrum, and collapse the data. Direct numerical simulations using a pseudo-solid sphere successfully reproduce experimental data whilst also providing insight into flow quantities that are challenging to determine from experiments. A model based on matching the motion of a perfectly hydrophobic impactor to a linearised fluid free surface is validated against direct numerical simulations and used in the low-Weber-number regime. The hierarchical and cross-validated models in this study allow us to explore the entirety of our target parameter space within a challenging multi-scale system.