Transient Effects in the Striped Phase of Nematic Liquid Crystals
A sudden application of an E or a B field normal to the director can lead to the formation of transient periodic structures. The appearance of the transient structures are due to backflow effects which couple the director and velocity fields, resulting in periodic instabilities. The final alignment of the director is uniform but the path to getting there involves a spatially periodic transient instability in which adjacent domains of the sample rotate in opposite senses.
A cell with 5CB is subjected to a single voltage step at fixed ac frequency in the presence of a stabilizing magnetic field. The cell is photographed at subsequent time intervals to follow the evolution of the transient structures. For a given B field and frequency, a voltage up to a critical value, causes 'static' patterns. Beyond this critical value, the patterns indicate turbulence.
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