Book Description

A dynamical description of atomic mixing in multicomponent gases and plasmas was summarized in a previous report (UCRL-ID-145502). That description is based on the use of separate continuity and momentum equations for each species present, including neutral atoms, ions, and free electrons. This level of detail is not always feasible in practical problems, where subsets of species (e.g., neutral atoms of a particular element together with their ionization products) must be grouped or lumped together into composite species or materials to make the problem tractable. A simple procedure for constructing such composite species was outlined in UCRL-ID-145502, but not in sufficient detail to enable implementation. In particular, the treatment of the free electrons presents some subtleties, since they cannot be included in the composite species for dynamical purposes, whereas they are ordinarily lumped together with the atoms and ions that produced them for state equation purposes. Our purpose here is to provide a more complete description of the procedure by which composite species and their evolution equations may be defined and derived. Special attention is given to the problem of how to deal with the free electrons in a manner consistent with the different roles they play in the dynamics and thermodynamics. The results are given in a form that should be well suited for implementation in hydrodynamics codes that use conventional material state equations.