Flow alignment in biaxial and discotic nematics

Continuum theory for nematic liquid crystals predicts two distinct types of flow alignment, one that observed in thermotropic rod-like nematics, and the second not so far observed but thought to be relevant to discotic nematics. This paper examines this latter possibility by considering recent flow alignment predictions for biaxial nematics, particularly for such materials where the molecular structure is close to discotic, and obtains results that support this claim. In addition it shows that in the disc-like limit biaxial theory reduces to that for a uniaxial nematic with viscosities consistent with this conjecture.