Two-dimensional, time-dependent, multigroup, multiangle radiation hydrodynamics test simulation in the core-collapse supernova context

We have developed a time-dependent, multi-energy group, multiangle (S _n) Boltzmann transport scheme for radiation hydrodynamics simulations in one and two spatial dimensions. The implicit transport is coupled to both one-dimensional (spherically symmetric) and two-dimensional (axially symmetric) versions of the explicit Newtonian hydrodynamics code VULCAN. The two-dimensional variant, VULCAN/2D, can be operated in general structured or unstructured grids, and although the code can address many problems in astrophysics, it was constructed specifically to study the core-collapse supernova problem. Furthermore, VULCAN/2D can simulate the radiation hydrodynamic evolution of differentially rotating bodies. We summarize the equations solved and methods incorporated into the algorithm and present the results of a time-dependent two-dimensional test calculation. A more complete description of the algorithm is postponed to another paper. We highlight a two-dimensional test run that follows the immediate postbounce evolution of a collapsed core for 22 ms. We present the relationship between the anisotropies of the overturning matter field and the distribution of the corresponding flux vectors as a function of energy group. This is the first two-dimensional multigroup, multiangle, time-dependent radiation hydrodynamics calculation ever performed in core-collapse studies. Although the transport module of the code is not gray and does not use flux limiters (however, there is a flux-limited variant of VULCAN/2D), it still does not include energy redistribution and most velocity-dependent terms.