Zou Hongyi, Zhang Dingwei, Fu Qingfei, Yang Lijun, Zheng Kaikai, Dong Ruo-Yu
School of Astronautics, Beihang University, Beijing 100191, China.
School of Astronautics, Beihang University, Beijing 100191, China; Aircraft and Propulsion Laboratory, Ningbo Institute of Technology, Beihang University, Ningbo 315100, China.
J Colloid Interface Sci. 2024 Dec;675:848-856. doi: 10.1016/j.jcis.2024.07.054. Epub 2024 Jul 9.
The scaling laws of drop pinch-off are known to be affected by drop compositions including dissolved polymers and non-Brownian particles. When the size of the particles is comparable to the characteristic length scale of the polymer network, these particles may interact strongly with the polymer environment, leading to new types of scaling behaviors not reported before.
Using high-speed imaging, we experimentally studied the time evolution of the neck diameter h of drops composed of silica nanoparticles dispersed in PEO solution when extruded from a nozzle.
After initial Newtonian necking with h ∼ t, the subsequent stage may exhibit scaling variation, characterized by either exponential or power-law decay, depending on the nanoparticle volume fraction ϕ. The exponential decay h ∼ e signifies the coil-stretch transition in typical viscoelastic suspensions. We conducted an analysis of the power-law scenario h ∼ t at high ϕ, categorizing the entire process into three distinct regimes based on the exponents α. The dependences of critical thicknesses at transition points and exponents on polymer concentration offer initial insights into the potential transition from heterogeneous to homogeneous thinning in the mixture. This novel scaling variation bears implications for accurately predicting and controlling droplet fragmentation in industrial applications.
已知液滴 pinch-off 的标度律会受到液滴成分的影响，包括溶解的聚合物和非布朗粒子。当粒子尺寸与聚合物网络的特征长度尺度相当时，这些粒子可能会与聚合物环境发生强烈相互作用，从而导致出现以前未报道过的新型标度行为。
我们使用高速成像技术，对从喷嘴挤出的、由分散在聚环氧乙烷（PEO）溶液中的二氧化硅纳米粒子组成的液滴颈部直径 h 的时间演化进行了实验研究。
在初始的 h ∼ t 的牛顿颈缩之后，后续阶段可能会呈现标度变化，根据纳米粒子体积分数 ϕ 的不同，其特征为指数衰减或幂律衰减。指数衰减 h ∼ e 表示典型粘弹性悬浮液中的线圈-拉伸转变。我们对高 ϕ 时 h ∼ t 的幂律情况进行了分析，根据指数 α 将整个过程分为三个不同的区域。转变点处的临界厚度和指数对聚合物浓度的依赖性，为混合物中从非均匀变薄到均匀变薄的潜在转变提供了初步见解。这种新颖的标度变化对于工业应用中准确预测和控制液滴破碎具有重要意义。
