Thixotropy in viscoplastic drop impact on thin films
Thixotropy in viscoplastic drop impact on thin films
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粘塑性液滴对薄膜影响的触变性
DOI：
10.1103/physrevfluids.6.043301
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发表时间：
2020
影响因子：
2.7
通讯作者：
R. Ewoldt
中科院分区：
文献类型：
--
作者：
S. Sen;Anthony G. Morales;R. Ewoldt
我们使用高速成像来研究触变老化对屈服应力流体对预涂基材的跌落影响的影响。我们的结果表明，与“未老化”样品相比，“老化”样品的液滴飞溅受到抑制，这表明冲击过程中的触变击穿时间尺度足够长，足以影响动力学。我们提出并测试了几个假设，用于修改无量纲组 ${\rm IF}(D/t)$ [1,2] 以解释触变老化。主要挑战是当前无量纲组中使用的稳定流动特性（Herschel-Bulkley 模型参数）无法针对触变老化样品进行定义或测量，因为任何变形都会固有地恢复并破坏微观结构。我们发现最合适的假设是仅根据老化样品的储能模量增加屈服应力（$\sigma_{\rm y}$，塑性成分），同时保持粘性参数（$K$ 或 $\eta_{\infty}$）恒定。这项工作揭示了对很少研究的具有触变效应的短时尺度流动条件的基本见解。这些结果对于涉及不同触变老化程度的复杂流体的灭火或喷涂等应用非常重要。
We use high-speed imaging to study the effect of thixotropic aging in drop impact of yield-stress fluids on pre-coated substrates. Our results reveal that drop splashing is suppressed for "aged" compared to "unaged" samples, indicating that thixotropic breakdown timescales during impact are long enough to affect the dynamics. We propose and test several hypotheses for modifying the dimensionless group ${\rm IF}(D/t)$ [1,2] to account for thixotropic aging. The main challenge is that the steady flow properties (Herschel-Bulkley model parameters) used in the current dimensionless group cannot be defined or measured for thixotropically aged samples, because any deformation inherently rejuvenates and breaks down the microstructure. We find the most suitable hypothesis is to only increase the yield stress ($\sigma_{\rm y}$, plastic component) based on the storage modulus of aged samples, while keeping the viscous parameters ($K$ or $\eta_{\infty}$) constant. The work reveals fundamental insight into rarely studied short-timescale flow conditions with thixotropic effects. These results are important for applications such as fire suppression or spray coating that involve complex fluids of varying degrees of thixotropic aging.
扩展屈服应力流体范式
影响因子：
3.3
作者：
Nelson, Arif Z.;Bras, Rafael E.;Liu, Jingping;Ewoldt, Randy H.
通讯作者：
Ewoldt, Randy H.