This talk focuses on the issues that arise when modeling and
simulating fluids containing rod--like molecules (nematics). The
(average) orientation of these fluids is typically modeled by a unit
vector field which complicates both the analysis and numerical
solution of these equations. In particular,
i) The unit length constraint gives rise to topological
singularities. While singularities are observed ubiquitously in
liquid crystals, classical models assign infinite elastic
energy to these configurations.
