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arXiv 2005.08132physics.flu-dyn
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液滴撞击球面的数值和理论模拟

Numerical and Theoretical Modeling of Droplet Impact on Spherical Surfaces

Hussein Dalgamoni, Xin Yong

备注：
42 pages, 14 figures
发表信息：
Physics of Fluids 33, 052112 (2021)
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摘要：

液滴对固体表面的冲击是增材制造、热管理和涂覆中广泛涉及的流体现象，其中对冲击动力学和持续时间施加控制的能力是至关重要的。虽然过去的研究已经建立了一个全面的了解的影响，平面基板上，我们知道的弯曲固体表面上的冲击动力学仍然是有限的。本文采用轴对称格子玻尔兹曼方法（LBM）和理论分析相结合的方法，研究了液滴在不同韦伯数（$We$）、半径（$R_s$）和表面润湿性（$θ^{eq}$）的球面上的撞击过程.在我们以前的工作[H. Dalgamoni和X. Yong，Phys.Rev.E98，13102（2018）]进行了扩展和修改，以模拟液滴在低韦伯数状态下（即，$We \leq 15$），其中液滴变形的轴对称假设成立。LBM模拟结果表明，$We$、$R_s$和$θ^{eq}$对液滴在撞击过程中的扩展和反冲有显著影响.参数研究揭示了五种影响结果，从完全沉积到完全反弹。模拟预测相图的构建和相关的总时间，液滴与固体接触。此外，还建立了一个基于撞击过程能量收支的理论模型，预测了不同We时撞击球形目标的反弹阈值，并与模拟结果进行了比较。这些研究结果提供了基本的洞察表面结构设计控制液滴流体动力学和接触时间在影响。

英文摘要：

Droplet impact on solid surfaces is a fluid phenomenon widely involved in additive manufacturing, heat management, and coating, in which the ability to exert control over the impact dynamics and duration is critical. While past studies have established a comprehensive understanding of the impact on flat substrates, what we know about the impact dynamics on curved solid surfaces is still limited. This work aims to elucidate the physics of droplet impact on spherical surfaces with different Weber numbers ($We$), radii ($R_s$), and surface wettability ($θ^{eq}$) using a combination of axisymmetric lattice Boltzmann method (LBM) and theoretical analysis. The model developed in our previous work [H. Dalgamoni and X. Yong, Phys. Rev. E 98, 13102 (2018)] was extended and modified for simulating the normal impact of droplet on curved substrates in the low Weber number regime (i.e., $We \leq 15$), in which axisymmetric assumption of droplet deformation holds. The LBM simulations show that $We$, $R_s$, and $θ^{eq}$ significantly affect the spreading and recoiling of droplet during impact. The parametric studies uncover five outcomes of impact, which range from complete deposition to total rebound. A simulation-predicted phase diagram was constructed and correlated with the total time that the droplet was in contact with the solid. In addition, a theoretical model based on energy budget during impact was developed to predict the rebound threshold for impact on spherical targets when varying We, and independently, which agrees well with simulation observations. These findings provide fundamental insight into surface structure design for controlling droplet hydrodynamics and the contact time during impact.

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