Pattern Formation in Nonequilibrium Dissipative Systems-Dynamics of Dissipative Structures in Liquid Crystals

非平衡耗散系统中的图案形成-液晶耗散结构动力学

基本信息

批准号：
10440117
负责人：
KAI Shoichi
金额：
$ 8.58万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1998
资助国家：
日本
起止时间：
1998 至 2000
项目状态：
已结题

项目摘要

The aim of this research project is to understand a role of system symmetries on pattern formations in nonequilibrium dissipative systems such as electrohydrodynamic instability (EHD) in nematic liquid crysals. In the EHD system, there are two different alignments ; planar and homeotropic ones. Regarding pattern formations in planar systems various new results have been obtained. Contrary to this, the study of EHD in homeotropic systems was very few, and no interesting results and no new physics were obtained so far. In the present study, we especially pay our attention to symmetries of the systems. Pattern formations in EHD strongly depend on the initial synmmetries of the systems, that is either on planar or homeotropic alignments. However the so-called chevron patterns appear independently of initial align-ments, i.e. initial symmetry of the system. Therefore we investigate at first the formation mechanism of this type of patterns. Then it is found that the chevron patterns are clas … More sified into four different types, chevron A and B, both of which are further classified into the patterns with periodic defect orientation(DMC) and defect free chevrons (DFC). DMC forms due to competitive instability between defect formation and director defomation similar to Turing instability. The mechanism of DFC in chevron A and B are unknown yet. It becomes however clear that the chevron patterns are fomed independently of boundary anchoring which always leads to no symmetry dependence in the pattern formation.Regarding EHD in a homeotropic alignment with a continuously rotational symmetry, a spatio-temporal chaos called the softmode turbulence (SMT) appears. SMT is a unique turbulence in a weakly nonlinear regime continuously connecting to a uniform stationary state via a single supercritical bifuraction and therefore expected to be understood precisely. This results from the additional Goldstone mode due to the continuously rotational symmetry, which can be suppressed by application of magnetic fields. The phase diagram has been obtained on a plane among the parameters of applied electric field intensity, its frequency and magnetic field strength. Two different STC's have been found out which depend on the symmetry of the system. Thus the small change of alignments (symmetries) leads to the big difference of pattern formations. The formation dynamics must be classified into two categories ; universal dynamics independent of symmetries and individual dynamics dependent on symmetries. Less

该研究项目的目的是了解系统对称性对非平衡耗散系统（例如向列液晶中的电流体动力学不稳定性（EHD））的影响。在 EHD 系统中，有两种不同的排列方式：与此相反，垂直系统中 EHD 的研究很少，没有获得有趣的结果，也没有获得新的物理结果。到目前为止，我们特别关注 EHD 中系统的对称性，这很大程度上取决于系统的初始对称性，即平面或垂直排列，但出现了所谓的 V 形图案。与初始排列无关，即系统的初始对称性，因此我们首先研究此类图案的形成机制，然后发现 V 形图案分为四种不同的类型。类型，V 形 A 和 B，由于与 DFC 的图灵不稳定性类似，缺陷形成和导向变形之间的竞争不稳定性进一步分为具有周期性缺陷取向（DMC）和无缺陷 V 形（DFC）形式。 V 形 A 和 B 中的 EHD 尚不清楚，但很明显，V 形图案的发泡独立于边界锚定，这始终导致图案形成中不存在对称性依赖性。关于垂直方向的 EHD。与连续旋转对称性对齐，出现了一种称为软模式湍流（SMT）的时空混沌，它是弱非线性状态中的一种独特湍流，通过单个超临界分岔连续连接到均匀稳态，因此有望被精确理解。这是由于连续旋转对称性而产生的额外戈德斯通模式，该模式可以通过施加磁场来抑制。相图是在所施加的电场强度参数的平面上获得的。已经发现两种不同的 STC 取决于系统的对称性，因此排列（对称性）的微小变化会导致图案形成的巨大差异。独立于对称性的普遍动力学和依赖于对称性的个体动力学 Less