[mesa-users] Implementing extra p & energy terms - EOS question

[Francis Timmes]

hi lewis,

my opening suggestion is to become a bit more familiar with 
the constituent equations of state (plural) used by mesa, 
the thermodynamic formalism and range of validity of each constituent,
and how mesa constructs its eos tables. section 4.1 of the mesa I 
instrument paper and appendix a.2 of mesa II can be useful starting points
for seeing options on how to proceed with potential modifications.

fxt



> On Sep 12, 2016, at 7:13 AM, Ireland, Lewis <lgi201 at exeter.ac.uk> wrote:
> 
> Hello,
> 
> This is a slightly different question to my previous, and might be easier to interpret.
> 
> I have an extra pressure term, P_mag, and an extra specific internal energy term, χ, that I want to implement, where P_mag ~ χ * Rho.
> 
> I have edited the momentum equation: dP/dm = dP_0/dm + dP_mag/dm, where P_0 = P_g + P_rad. The energy transport/conservation equations are unchanged in this case.
> 
> Because P_mag performs no work, the first law of thermodynamics is:
> 
> dQ = Tds = dU + P_0 dV - P_mag dV
> 
> How do I modify the eos in MESA in order to fulfil this modified law, as dQ = Tds = dU + P_tot dV is what I am presuming to be “performed" at the moment, which is incorrect as it includes P_mag?
> 
> Cheers,
> 
> Lewis
> 
> P.S. If I am successful with the above, will this modify the specific internal energy (by adding χ) through this treatment, or would I need to add χ manually to U?
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