REOROM Laboratory, Faculty of Energy Engineering, University Politehnica of Bucharest, Splaiul Independentei 313, 060042, Bucharest, Romania.
Sci Rep. 2022 Feb 2;12(1):1774. doi: 10.1038/s41598-022-05839-y.
The dripping regime in the vicinity of the fluid droplet breakup is analyzed using the correlation between experiments and numerics. The evolutions of filament's neck and its corresponding thinning velocity are described using the logistic functions. Three flow regions are observed as the relative time decreases: (1) a monotonous increase of the neck's thinning velocity, where inertia and capillarity are balanced, (2) a transition domain characterized by the equilibrium between inertia, capillarity, and viscous forces, where the thinning velocity varies non-monotonically with the relative time and (3) the final droplet pinch-off, where velocity decreases or oscillates around a constant value. The distributions of the [Formula: see text]-coefficient (parameter related to the non-dimensional second invariant of the velocity gradient) on the filament's surface and droplet's profile characterize the kinematics at the interface. The regions dominated by extension, where pure elongation is located at [Formula: see text], are determined. One main result of this study is the confirmation that distribution of the [Formula: see text]-coefficient is a relevant parameter to analyze and to quantify the breakup process. This result has the potential of developing novel techniques and more precise procedures in determining the interfacial rheology of viscous and complex fluids.
使用实验和数值之间的相关性来分析液滴断裂附近的滴落状态。使用逻辑函数描述细丝颈部及其相应的变薄速度的演变。随着相对时间的减少，观察到三个流动区域：（1）颈部变薄速度的单调增加，其中惯性和表面张力达到平衡；（2）以惯性、表面张力和粘性力之间的平衡为特征的过渡区域，其中变薄速度随相对时间呈非单调变化；（3）最终的液滴断裂，其中速度降低或围绕恒定值振荡。在纤维表面和液滴轮廓上的[Formula: see text]-系数（与速度梯度的无量纲第二不变量有关的参数）分布特征化了界面处的运动学。确定了由扩展主导的区域，其中纯伸长位于[Formula: see text]处。这项研究的一个主要结果是证实了[Formula: see text]-系数的分布是分析和量化断裂过程的一个相关参数。该结果有可能开发出用于确定粘性和复杂流体的界面流变学的新技术和更精确的程序。
