  The potential for laser-produced plasmas to yield fundamental insights into
high energy density physics (HEDP) and deliver other useful applications can
sometimes be frustrated by uncertainties in modeling the properties and
expansion of these plasmas using radiation-hydrodynamics codes. In an effort to
overcome this and to corroborate the accuracy of the HEDP capabilities recently
added to the publicly available FLASH radiation-hydrodynamics code, we present
detailed comparisons of FLASH results to new and previously published results
from the HYDRA code used extensively at Lawrence Livermore National Laboratory.
We focus on two very different problems of interest: (1) an Aluminum slab
irradiated by 15.3 and 76.7 mJ of "pre-pulse" laser energy and (2) a mm-long
triangular groove cut in an Aluminum target irradiated by a rectangular laser
beam. Because this latter problem bears a resemblance to astrophysical jets,
Grava et al., Phys. Rev. E, 78, (2008) performed this experiment and compared
detailed x-ray interferometric measurements of electron number densities to
HYDRA simulations. Thus, the former problem provides an opportunity for
code-to-code comparison, while the latter provides an opportunity for both
code-to-code comparison and validation. Despite radically different schemes for
determining the computational mesh, and different equation of state and opacity
models, the HYDRA and FLASH codes yield results that are in excellent agreement
for both problems and with the experimental data for the latter. Having
validated the FLASH code in this way, we use the code to further investigate
the formation of the jet seen in the Grava et al. (2008) experiment and discuss
its relation to the Wan et al. (1997) experiment at the NOVA laser.
