  We present a lattice Boltzmann solution of the equations of motion describing
the spreading of droplets on topologically patterned substrates. We apply it to
model superhydrophobic behaviour on surfaces covered by an array of
micron-scale posts. We find that the patterning results in a substantial
increase in contact angle, from $110^o$ to $156^o$. The dynamics of the
transition from drops suspended on top of the posts to drops collapsed in the
grooves is described.
