PATTERN DYNAMICS IN THE ELECTROHYDRODYNAMICS OF NEMATIC LIQUID-CRYSTALS - DEFECT PATTERNS, TRANSITION TO TURBULENCE AND MAGNETIC-FIELD EFFECTS
PATTERN DYNAMICS IN THE ELECTROHYDRODYNAMICS OF NEMATIC LIQUID-CRYSTALS - DEFECT PATTERNS, TRANSITION TO TURBULENCE AND MAGNETIC-FIELD EFFECTS
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DOI：
10.1143/ptps.99.458
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发表时间：
1989-01-01
影响因子：
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通讯作者：
ZIMMERMANN, W
中科院分区：
文献类型：
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作者：
KAI, S;ZIMMERMANN, W
研究了平面排列向列相液晶电流体动力对流的各种模式。给出了导电区和介电区对流开始的实验和理论结果。详细描述了导流区对流开始上方的起伏威廉斯域(FWD)的转变。在此二次门槛时，直轧辊变得不稳定，出现缺陷。在FWD的时间发展过程中，缺陷不断地产生和消失，并且缺陷密度在时间上表现出较强的随机性。在更高的外加电压下，我们研究了两个湍流态DSM1和DSM2之间的跃迁，这与超流HeII中的TI-TII跃迁有一定的相似之处。DSM-2湍流的特征是倾斜性，因此称为倾斜性湍流。我们证明了这种相变是通过成核的局域性的，并且两种态之间的主要区别在于DSM1态的零位错密度和DSM2态的有限值。在高频区，我们将二次跃迁分析为周期缺陷结构，并分析了该图形中的缺陷动力学。此外，还考虑了叠加磁场对这些图案的影响。
Various patterns in the electrohydrodynamic convection of planarly aligned nematic liquid crystals are investigated. We give experimental and theoretical results on the onset of convection in the conduction regime and the dielectric regime as well. The transition to the fluctuating Williams domain (FWD) immediately above the onset of convection in the conduction regime is characterized in detail. At this secondary threshold the straight rolls become unstable and defects appear. During the temporal development of the FWD, defects are continuously created and annihilated, and the defect density behaves rather stochastical in time. At even higher values of the applied voltage we investigate the transition between the two turbulent states DSM1 and DSM2 which has some analogy with TI-TII transition in superfluid HeII. DSM 2 turbulence can be characterized by disclination and therefore called disclination turbulence. We show that this transition is local via nucleation and that the main difference between both states is the vanishing disclination density in the DSM1 state and its finite value in the DSM2. In the high frequency regime we analyse the secondary transition to chevrons and the defect dynamics in this pattern as a periodic defect structure. Furthermore, the influence of a superimposingly applied magnetic field on these patterns is considered.