Rupture Dynamics and Buckling Instabilities of Free-Standing Liquid Crystal Bridges and Filaments

一维的、独立的流体结构在自然界中并不常见，但可以由任何能够克服毛细（瑞利-高原）不稳定性的材料形成。一旦这种不稳定性被抑制，长纤维，与长度直径比超过1000，可能会形成。早期的报告，独立的液晶丝和桥测量其机械，声学和电气稳定性。另一个重要的方面，很少有报道，是不稳定性的影响，导致断裂或导致长丝在压缩应力下弯曲。在食品工业中，为了控制大规模生产的液体薄片或液体绳，对这些过程的定量认识是必要的。能够形成稳定细丝的物质具有某种内部结构。由此产生的断裂和屈曲动力学比粘性牛顿流体复杂得多。在本研究计划中，我们计划系统地研究夹断，断裂动力学，屈曲不稳定性，以及由dissolved和dissolved-core液晶形成的细丝的流动特性。液晶是独特的，因为它们的性质很大程度上取决于存在的取向和位置有序的量。这一性质使液晶区别于其他粘性非牛顿流体。我们试图回答的一些问题如下：变薄、夹断和破裂过程的动力学是什么？在断裂过程中，桥或细丝上和内部的拓扑缺陷是如何演变的？它们对破裂过程有什么影响？这种结构化过程与弹性力（方向力和位置力）有什么关系？

One-dimensional, free-standing fluid structures are not often found in nature, but may be formed by any material that can overcome capillary (Rayleigh-Plateau) instability. Once this instability is suppressed, long filaments, with length-to-diameter ratios exceeding 1000, may be formed.Earlier reports on free-standing liquid crystal filaments and bridges measured their mechanical, acoustical, and electrical stability. Another important aspect, on which there are few reports, is the effect of instabilities that lead to rupture or cause the filament to buckle under compression stress. Quantitative knowledge of such processes has found necessity in the food industry for controlling large liquid sheets or ropes for mass production.Substances capable of forming stable filaments have some sort of internal structure. The resulting rupture and buckling dynamics are substantially more complicated than those for viscous Newtonian fluids.In this research program, we plan to systematically study the pinch-off, rupture dynamics, buckling instabilities, and flow characteristics of filaments formed from discotic and bent-core liquid crystals. Liquid crystals are unique because their properties depend greatly on the amount of orientational and positional ordering present. This property distinguishes liquid crystals from other viscous non-Newtonian fluids.Some of the questions we seek to answer are as follows:What are the dynamics of the thinning, pinch-off, and rupture process?How do topological defects on and within the bridge or filament evolve during the rupture process? What effect do they have on the rupture process?How do such structuring processes relate to the elastic forces (orientational and positional)?