Threshold orientation transition in nematic liquid crystals under ultrasonic action

The adequacy of the new theoretical model based on the ideas of nonequilibrium thermodynamics and nonlinear hydrodynamics of liquid crystals for describing the mechanism of threshold reorientation of molecules in a homeotropically oriented layer of a nematic liquid crystal under the effect of a cross-homogeneous ultrasonic wave is experimentally substantiated. It is demonstrated that (i) the critical particle velocity is inversely proportional to the layer thickness, (ii) its relation to the frequency of oscillations is ambiguous and depends on the relation between the ultrasonic frequency and the inverse relaxation time of the orientation order parameter, and (iii) the stationary distortion of microstructure is homogeneous along the layer.