In this work, the impact dynamics of high-viscous nanofluid droplets onto a solid surface has been investigated experimentally by means of high-speed camera visualization technique. We dispersed various nanoparticles (multiwall carbon nanotube (MWCNT), nano-graphene, and nano-graphite powder) into high-viscous base fluid (epoxy resin) to obtain the stable and homogenous nanofluids without surfactant additives. The well dispersed nanofluids show different degree of shear-thinning behaviors, and the shear-thinning properties of those fluids have been characterized by the power-law rheology model. The dynamic contact angle (DCA), transient dimensionless height, and transient contacting factor along with the spreading time under different Weber numbers (We) have been investigated. The results show that the nanofluid with a lower shear viscosity over the entire range of the shear rates results in larger variations of the contacting factor and the dimensionless height. The effect of surface wettability on droplet impact behaviors is more significant for the fluid with higher shear viscosity and less shear-thinning degree during the receding phase. The latter spreading and receding motions of the droplet with higher shear viscosity and shear-thinning degree are suppressed significantly, regardless of the Weber numbers in current study. Finally, a model based on experimental data has been proposed to predict the maximum spreading factor of high-viscous droplet impact on solid surface.

中文翻译：

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高粘度纳米流体液滴的扩散行为影响固体表面

在这项工作中，已经通过高速相机可视化技术实验研究了高粘度纳米流体液滴对固体表面的冲击动力学。我们将各种纳米颗粒（多壁碳纳米管（MWCNT），纳米石墨烯和纳米石墨粉）分散到高粘度基础液（环氧树脂）中，从而获得了稳定且均质的纳米流体，而没有表面活性剂添加剂。分散良好的纳米流体表现出不同程度的剪切稀化行为，并且已经通过幂律流变模型表征了这些流体的剪切稀化特性。研究了在不同韦伯数（We）下的动态接触角（DCA），瞬态无因次高度和瞬态接触因子以及扩展时间。结果表明，在整个剪切速率范围内具有较低剪切粘度的纳米流体导致接触系数和无因次高度的较大变化。对于在后退阶段具有较高剪切粘度和较小的剪切稀化度的流体，表面润湿性对液滴冲击行为的影响更为显着。不管当前研究中的韦伯数如何，具有较高剪切粘度和剪切稀化度的液滴的后者的扩展和后退运动均得到显着抑制。最后，基于实验数据的模型已经被提出来预测高粘度液滴对固体表面的最大扩散因子。对于在后退阶段具有较高剪切粘度和较小的剪切稀化度的流体，表面润湿性对液滴冲击行为的影响更为显着。不管当前研究中的韦伯数如何，具有较高剪切粘度和剪切稀化度的液滴的后者的扩展和后退运动均得到显着抑制。最后，提出了一个基于实验数据的模型来预测高粘度液滴对固体表面的最大扩散因子。对于在后退阶段具有较高剪切粘度和较小的剪切稀化度的流体，表面润湿性对液滴冲击行为的影响更为显着。不管当前研究中的韦伯数如何，具有较高剪切粘度和剪切稀化度的液滴的后者的扩展和后退运动均得到显着抑制。最后，提出了一个基于实验数据的模型来预测高粘度液滴对固体表面的最大扩散因子。无论当前研究中的韦伯数如何。最后，提出了一个基于实验数据的模型来预测高粘度液滴对固体表面的最大扩散因子。无论当前研究中的韦伯数如何。最后，基于实验数据的模型已经被提出来预测高粘度液滴对固体表面的最大扩散因子。