[Mesa-users] Query regarding implementing hydrodynamics

[Ebraheem Farag]

Hello Abha,

I don't have a whole lot to say here beyond "Here be dragons".

In the current form we only use the HLLC rieman solver for explosion
modeling, not normal evolution calculations.
Perhaps investigate the $MESA_DIR/star/test_suite/PPISN test_suite to get
an idea for what might be needed to get rieman hydro working during a
normal evolution run with the core intact.
Also note that this was only done for very short timescales and a large
mesh with tight time steps might be necessary to get anywhere. Sometimes
the numerical initialization of riemann hydro can even drive the surface
crazy as well if done during an evolution calculation. I have some working
fixes for this but they are quite involved and do not exist in the current
release version. Just know that we're working on it and we'll likely
implement a future test suite to showcase how it's done :).

-EbF

On Fri, Mar 8, 2024 at 5:15 AM Abha Vishwakarma via Mesa-users <
mesa-users at lists.mesastar.org> wrote:

> Dear MESA Users,
>
> I have been trying to switch on hydrodynamics in a 12 solar mass red giant
> star. I first ran the hse_reimann test suite which implements
> hydrodynamics in a 12 solar mass star with the core excised. But, I wish to
> implement hydrodynamics with the core intact.
>
> I switched on hydrodynamics by adding the following lines to my inlist:
>
>         change_initial_u_flag = .true.
>     change_initial_v_flag = .true.
>     new_v_flag = .false.
>     new_u_flag = .true.
>
> My program takes as input a 12 solar mass red giant. But, the program
> crashes because it hits the timestep limit or because of crossing some
> tolerances. But, if I instead take the 12 solar mass star with the core
> removed, as is done in the hse_reimann module, the code works fine.
>
> I am not sure what I am missing here, but I feel it has something to do
> with the core of the red giant, or some boundary conditions or physics that
> I might have missed. I have attached my inlist to this email, and any help
> in this regard would be greatly appreciated!
>
> Sincerely,
> Abha Vishwakarma
> _______________________________________________
> mesa-users at lists.mesastar.org
>
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