Variational theory for nematoacoustics

The effect of an ultrasonic wave on the nematic texture has long been known, but its interpretation in terms of a coherent dynamical theory has not yet been achieved. A proposal for such a theory is made in this paper. The diverse theoretical approaches attempted in the past to describe the interaction between sound and nematic molecular orientation are briefly summarized. A theory for second-grade fluids, which provides the appropriate theoretical background for nematoacoustics, is also revived. An explicit application of the proposed theory to a simple computable case is given, which yields predictions that are qualitatively confirmed by a number of experimental results.