On modelling CC85 wind in an expanding local box
  The Chevalier & Clegg (1985) spherical wind is widely used to model galactic
outflows. Efforts are underway to understand the production of multiphase gas
in such outflows. Since the important scales for the multiphase gas are very
small compared to the size of the wind, it is very useful to have a local model
of the cold gas interacting with a volume-filling expanding wind. In this note
we explicitly derive the governing hydrodynamic equations in such a local box
for the first time. We highlight that the expansion in a wind occurs only in
the transverse direction, and this results in anisotropic source terms in the
momentum equation. Our equations will be very useful in realistic modelling of
the small scale structure of multiphase galactic outflows. [original note does
not include an abstract]
