Torsional instability of constant viscosity elastic liquid bridges
Torsional instability of constant viscosity elastic liquid bridges
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DOI：
10.1039/d1sm01804c
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发表时间：
2022-02-07
期刊：
影响因子：
3.4
通讯作者：
Shen, Amy Q.
中科院分区：
文献类型：
--
作者：
Chan, San To;Varchanis, Stylianos;Shen, Amy Q.
通过实验和模拟，我们报道了由恒粘弹性液体制成的粘弹性液桥。Boger流体，可以有效地因扭转而不稳定。在扭转作用下，液桥的变形取决于弹性毛细效应和扭转诱导的正应力效应之间的竞争。当弹性毛细管效应占主导地位时，液桥经历弹性毛细管不稳定性，变薄为圆柱形丝线，其长度增加，半径随时间呈指数衰减。当扭转引起的正应力效应占主导地位时，液桥以类似于边缘断裂的方式变形，这种流动不稳定的特征是当粘弹性流体以高于临界变形速率的速度剪切时，流体的自由表面突然凹陷。法向应力的垂直分量使液桥的上下部分相互靠近，而径向应力的径向分量导致液桥变薄的速度比弹性毛细作用下的要快。这种快速减薄是否会持续到桥断裂，取决于液桥的配置和所施加的扭转程度。
By experiment and simulation, we report that viscoelastic liquid bridges made of constant viscosity elastic liquids, a.k.a. Boger fluids, can be effectively destabilized by torsion. Under torsion, the deformation of the liquid bridge depends on the competition between elastocapillarity and torsion-induced normal stress effects. When the elastocapillary effect dominates, the liquid bridge undergoes elastocapillary instability and thins into a cylindrical thread, whose length increases and whose radius decays exponentially over time. When the torsion-induced normal stress effect dominates, the liquid bridge deforms in a way similar to edge fracture, a flow instability characterized by the sudden indentation of the fluid's free surface when a viscoelastic fluid is sheared at above a critical deformation rate. The vertical component of the normal stress causes the upper and lower portions of the liquid bridge to approach each other, and the radial component of the normal stress results in the liquid bridge thinning more quickly than under elastocapillarity. Whether such quick thinning continues until the bridge breaks depends on both the liquid bridge configuration and the level of torsion applied.