论文标题
表面粘性应力对装有几乎被关联表面活性剂的自由表面的捏合的影响
Influence of the surface viscous stress on the pinch-off of free surfaces loaded with nearly-inviscid surfactants
论文作者
论文摘要
我们在理论上和实验上分析了装有十二烷基硫酸钠（SDS）的吊坠水滴的分裂。将实验中测得的自由表面最小半径与从全navier-Stokes方程的数值解相比，用于不同值的剪切和扩张表面粘度。该比较显示了表面粘性应力对系统动力学的较小但可测量的效果，该动力学与分解点相距足够小的时空距离，并允许为剪切和扩张粘度的值建立上限。我们从数值上研究Marangoni和粘性应力在自由表面上的分布，这是捏合时间的函数，并描述当自由表面接近其破裂时，捏合区域中表面粘应力如何生长。当考虑到Marangoni和表面粘度应力时，在分析的时间间隔内不会将表面活性剂扫除螺纹颈部。表面粘性应力最终平衡了该区域的驾驶毛细管压力，以捏合足够的时间。基于此结果，我们提出了一个缩放定律，以说明表面粘度对颈部半径时间进化的最后阶段的影响。
We analyze both theoretically and experimentally the breakup of a pendant water droplet loaded with Sodium Dodecyl Sulfate (SDS). The free surface minimum radius measured in the experiments is compared with that obtained from a numerical solution of the full Navier-Stokes equations for different values of the shear and dilatational surface viscosities. This comparison shows the small but measurable effect of the surface viscous stresses on the system dynamics for sufficiently small spatiotemporal distances from the breakup point, and allows to establish upper bounds for the values of the shear and dilatational viscosities. We study numerically the distribution of Marangoni and viscous stresses over the free surface as a function of the time to the pinching, and describe how surface viscous stresses grow in the pinching region as the free surface approaches its breakup. When Marangoni and surface viscosity stresses are taken into account, the surfactant is not swept away from the thread neck in the time interval analyzed. Surface viscous stresses eventually balance the driving capillary pressure in that region for small enough values of the time to pinching. Based on this result, we propose a scaling law to account for the effect of the surface viscosities on the last stage of the temporal evolution of the neck radius.
