Introduction

Several multidimensional computations of hydrodynamics related to supernovae have been completed, and are summarized here. More detail may be found in Arnett 1994a,b, Arnett & Livne 1994a,b, and Livne & Arnett 1993. The hydro code PROMETHEUS is based upon an implementation of the piecewise-parabolic method (PPM) of Colella & Woodward 1984, as described in Fryxell et al. 1991. A detailed comparison of PPM with other schemes is given in Woodward & Colella 1984. The method constructs the physics of the flow between grid points by a nonlinear solution of the equations of continuity of mass, momentum and energy (the Riemann problem) rather than the usual mathematical approach of a Taylor expansion about the grid points. This gives it better resolution per grid point, which is highly desirable for multidimensional problems. Although the effort required per grid point is greater, the number of such points is less (often much less) for a given level of accuracy. Because the computational load per grid point is greater, more realistic physics (reactions, radiation, gravity, etc.) may be added before affecting the runtime significantly. Thus PPM is well suited for multidimensional problems with significant physics beyond the bare hydrodynamics.

The Prometheus project was an effort by the author, Bruce Fryxell and Ewald Müller, to implement a “state of the art” hydrodynamic method with realistic microphysics for stellar problems. After an extensive study of several methods, and direct comparison of the resulting codes (Fryxell, Müller & Arnett 1989), PPM was chosen as the preferred method.