  The development of radiation hydrodynamical methods that are able to follow
gas dynamics and radiative transfer self-consistently is key to the solution of
many problems in numerical astrophysics. Such fluid flows are highly complex,
rarely allowing even for approximate analytical solutions against which
numerical codes can be tested. An alternative validation procedure is to
compare different methods against each other on common problems, in order to
assess the robustness of the results and establish a range of validity for the
methods. Previously, we presented such a comparison for a set of pure radiative
transfer tests (i.e. for fixed, non-evolving density fields). This is the
second paper of the Cosmological Radiative Transfer (RT) Comparison Project, in
which we compare 9 independent RT codes directly coupled to gasdynamics on 3
relatively simple astrophysical hydrodynamics problems: (5) the expansion of an
H II region in a uniform medium; (6) an ionization front (I-front) in a 1/r^2
density profile with a flat core, and (7), the photoevaporation of a uniform
dense clump. Results show a broad agreement between the different methods and
no big failures, indicating that the participating codes have reached a certain
level of maturity and reliability. However, many details still do differ, and
virtually every code has showed some shortcomings and has disagreed, in one
respect or another, with the majority of the results. This underscores the fact
that no method is universal and all require careful testing of the particular
features which are most relevant to the specific problem at hand.
