Modeling liquid droplet impact on a micropillar-arrayed viscoelastic surface via mechanically averaged responses
Modeling liquid droplet impact on a micropillar-arrayed viscoelastic surface via mechanically averaged responses
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DOI：
10.1080/19942060.2023.2194949
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发表时间：
2023-04
影响因子：
6.1
通讯作者：
Yang Li;Jiangtao Cheng
中科院分区：
文献类型：
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作者：
Yang Li;Jiangtao Cheng
液滴撞击衬底是一种有趣的现象，广泛存在于我们的日常生活和广泛的工业过程中。然而，液滴在柔软纹理表面上的碰撞动力学研究较少，其潜在机制仍然难以捉摸。本文用Basilisk软件对微柱排列的软表面上的液滴撞击动力学进行了数值模拟，其中包括一个多尺度的几何区域，其中微柱和液滴的大小分别为μm和mm。因此，流体体积法(VOF)与有限体积法(FVM)相结合来建立流场并跟踪它们的界面。从概念的角度来看，微柱撑衬底是通过将间隙施加到原本完整的软材料中而形成的，其粘弹性性能可以用间隙密度ϵ来量化。通过一个五参数广义Maxwell模型，微柱衬底的粘弹性特性可以用其在Laplace-Carson(LC)空间中的等效弹性响应来近似，并通过LC逆变换得到微柱衬底在实空间中的平均体应变。此外，通过对飞溅程度的参数研究，发现对于特定的ϵ，飞溅随着撞击速度的增加而显著增强。随着环境压力的增加，飞溅也变得更加剧烈，在5atm处，喷射板与水平衬底之间的飞溅角为114.44美元/114.44∘，证明了这一点。相反，随着表面张力σ的增加，飞溅变得更加压抑。总体而言，我们模拟的飞溅量与开尔文-亥姆霍兹不稳定性理论所预测的一致。通过利用流体-粘弹性固体相互作用中的LC变换，我们的模拟方法通过机械平均响应来捕捉微结构粘弹性表面上液滴碰撞动力学的主要特征，同时避免了区域尺度不一致的困境。
Droplet impact on a substrate is an intriguing phenomenon that widely exists in our daily life and a broad range of industrial processes. However, droplet impact dynamics on soft textured surfaces are less explored and the underlying mechanisms remain elusive. Here, we report numerical simulation of droplet impact dynamics on a micropillar-arrayed soft surface using BASILISK, which involves a multiscale geometric domain containing the micropillars and droplet that are in the order of $ \rmu {\rm m} $ μm and $ {\rm mm} $ mm, respectively. As such, the volume of fluid (VOF) method is coupled with the finite volume method (FVM) to build the fluid fields and track their interface. From a conceptual point of view, the micropillared substrate is formed by imposing interstitial gaps into the otherwise intact soft material, whose viscoelastic properties can be quantified by gap density ϵ. Via a five-parameter generalized Maxwell model, the viscoelastic properties of the micropillared substrate can be approximated by its equivalent elastic response in the Laplace–Carson (LC) space, and the averaged bulk strain of the micropillared substrate in the real space is obtained by the inverse LC transform. Moreover, through parametric studies of splash extent, it turns out that for a specific ϵ, the splash is dramatically intensified with increasing impact velocity $ U_i $ Ui. The splash also turns more violent with increasing ambient pressure $ P_a $ Pa, which is evidenced by a larger splash angle of $ 114.44^\circ $ 114.44∘ between the ejected sheet and the horizontal substrate at 5 atm. Conversely, the splash becomes more depressed with increasing surface tension σ. Overall, the splash magnitudes of our simulations agree well with those predicted by the Kelvin-Helmholtz instability theory. By leveraging the LC transform in the fluid-viscoelastic solid interactions, our simulation methodology captures the main features of droplet impact dynamics on microstructured viscoelastic surfaces by means of the mechanically averaged responses while avoiding the predicament of domain scale inconsistency.