Different Types of Low-Frequency Electrohydrodynamics

References [59] investigate the static and dynamic behavior of the electrohydrodynamic instability in fireely suspended layers of nematic liquid crystals. The existence of a domain mode was shown, which consists of adjacent elongated domains with a spatial period proportional to the thickness of the layer. This mode occurs only if the thickness of the layer exceeds a critical value 7 /x), and can be understood in terms of the same anisotropic mechanism as the Carr-Helfrich-type, as in the case of the Kapustin-WiUiams modulated structure. 

Of special interest is the case where the electrohydrodynamic instability is caused by a spatially periodic external field. Then there begins an interplay of two periods, the period of the vortex structure w d and the field period A which may be varied in experiment [61]. In such a situation the resulting period of the domain structure may be either commensurate or incommensurate with the field period. So, using electrohydrodynamic patterns with a controlled period, e.g., by a change in the layer thickness, it is possible to model the appearance of different phases in the physical systems, investigate the motion of solitary waves, etc. [62]. 

FIGURE 5.9. Electrohydrodynamic instability with tilted director orientations at the boundaries [63]. 

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