[FLASH-USERS] Fwd: FLASH code EoS

[Klaus Weide]

Dear Prof. Lanzafame,

I am responding to your message asking about EoS in FLASH and cc'ing the 
flash-users mailing list, since this may be useful for others.

You wrote:
> I write you because I need some information about the equation of state
> used in the FLASH code.
> Guessing that they are several and referring to a plasma flow, I need to
> know what
> physical/chemical are taken into account, e.g. mass density, temperature
> and so on. It is possible
> that they are more. I ask this because, reading the published papers,
> since the EoS is in the form
> of tables I do not know how they have been written.

FLASH provides several variants of EoS, in the form of implementations of 
the "Eos" code unit.

Besides simpler implementations based on ideal-gas assumptions, which are 
named "Gamma" and "Multigamma", there are two different implementations
based on tables:

 1) "Helmholtz" implementation, for plasma at temperatures > 10000 K,
    based (for the electron component) on material-independent tables 
    that hold the Helmholtz free energy and derivative as 
    functions of (density,temperature).
    This is used (mostly) in 1-T astrophysical simulations.

 2) "Tabular" implementations for materials in multi-temperature (3-T)
    configuration.
    These are most often used for simulating high-energy density 
    laboratory experiments.
    Different materials can be described by different collections of 
    tables. Tables hold Z, e_ele, e_ion, p_ele, p_ion as functions 
    of ([number] density,temperature).  The public FLASH code reads
    in tables in IONMIX format; other formats have to be converted
    before FLASH can used them.

 Both forms of Eos implementations can depend on composition, which
 in FLASH is described as a set of mass fraction fields (which are
 advected by the hydro or MHD implementation).


All of this is described in the FLASH 4.4 User's Guide, which is available
online from our Support page at

  http://flash.uchicago.edu/site/flashcode/user_support/ .

See in particular (in either the PDF or HTML version linked on that page) 

  Chapter 16. Equation of State Unit,

which includes sections you may be particularly interested in:

  ...
  16.3 Helmholtz
  ...
  16.4 Multitemperature extension for Eos
    ...
    16.4.3 Tabulated
    ...

Please feel free to ask if you would like further clarification;
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Klaus