APACHE: a generalized-mesh Eulerian computer code for multicomponent chemically reactive fluid flow

TL;DR: The APACHE computer code has been developed to solve the equations of transient multicomponent chemically reactive fluid dynamics, using a new difference approximation to the convective terms, the tensor viscosity method, to achieve numerical stability without excessive numerical damping.

Abstract: The APACHE computer code has been developed to solve the equations of transient multicomponent chemically reactive fluid dynamics. APACHE is a time-marching finite-difference code that can be run in a purely explicit mode or a partially implicit (ICE) mode. The governing equations are written in two-dimensional variable-depth form. This description includes planar and cylindrical geometries as special cases. Spatial differences are written in conservative form wherever possible, using a generalized two-dimensional Eulerian mesh that allows convenient representation of curved boundaries and provides variable zoning. A new difference approximation to the convective terms, the tensor viscosity method, is used to achieve numerical stability without excessive numerical damping. Multicomponent diffusion is calculated by a self-consistent effective binary diffusion algorithm. APACHE contains a spatial marching option that greatly reduces computer time for steady-state supersonic flow calculations. For CW chemical laser applications, radiation intensities and laser power are calculated. The radiation intensities are fully coupled to the fluid, so that threshold, cutoff, and J-shifting occur automatically. Complete descriptions of the APACHE methodology, the code structure, and the procedure for setting up problems are provided. A FORTRAN listing of the code is given in an appendix.