  We present a mesoscopic lattice model for non-ideal fluid flows with
directional interactions, mimicking the effects of hydrogen-bonds in water. The
model supports a rich and complex structural dynamics of the orientational
order parameter, and exhibits the formation of disordered domains whose size
and shape depend on the relative strength of directional order and thermal
diffusivity. By letting the directional forces carry an inverse density
dependence, the model is able to display a correlation between ordered domains
and low density regions, reflecting the idea of water as a denser liquid in the
disordered state than in the ordered one.
