[Mesa-users] Using other_momentum in Riemann solver

[Josiah Schwab]

Hello Jing-Ze,

I was wondering how the other_pressure routine enters MESA r15140.
> When I grep into star/private for extra_pressure I get this message:
> grep -rin extra_pressure *.f90
>
> alloc.f90:1027:            call do1(s% extra_pressure, c% extra_pressure)
> alloc.f90:1028:            if (failed('extra_pressure')) exit
> hydro_energy.f90:623:            if (s% use_other_pressure) PR_18%val =
> PR_18%val + s% extra_pressure(k-1)
> hydro_energy.f90:647:         if (s% use_other_pressure) PL_18%val =
> PL_18%val + s% extra_pressure(k)
> star_utils.f90:3370:         if (s% use_other_pressure) XP_18%val =
> XP_18%val + s% extra_pressure(k)
>
> And I am not sure how to interpret these.
> The main questions I want to ask are:
>
> 1. Is s% extra_pressure a P_extra so that P_total = P_rad + P_gas +
> P_extra ? When I refer to s% P(k), is it correct that I get P_total?
>
> 2. If so, can extra_pressure automatically enter the momentum equation and
> energy equation in Riemann solver?
>
> 3. Will this extra_pressure affects thermodynamic quantities?
>

Your search for a key string (followed by reading the surrounding code) is
a good strategy for understanding what happens inside MESA.

As you showed, the way in which extra_pressure enters the equations is
quite limited, and so the answers to your questions 1-3 are no.

Josiah
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