[Mesa-users] WD and accretion material artificially mixing due to mesh adjustment

[Evan Bauer]

Hi Arman,

Can you quantify for us how far inward in mass the the accreted material travels due to artificial mixing from mesh adjustment? My guess would be that it’s less than what you would get if you turned on element diffusion (a physical process), so I’m not sure it’s quite right to say that this is “not physically possible”.

Still, if you want to minimize the impact of this artificial mixing, it would probably be helpful to increase the spatial resolution at the surface before you start accreting. Maybe try decreasing “mesh_delta_coeff” and also have a look at the control “max_surface_cell_dq”. You could also look at the inlists in the “wd_cool” test suite for an example of increasing the surface resolution before going on to do the actual run.

Cheers,
Evan


> On Sep 27, 2018, at 10:40 AM, Arman via Mesa-users <mesa-users at lists.mesastar.org> wrote:
> 
> Hello MESA-users,
> 
> I’m using MESA to simulate Novae explosions for my masters project, for which I use a carbon 12, oxygen 16 white dwarf model of mass 1.0000127678359980 M_sun and 528 shells. My problem is that once MESA starts accreting solar material onto the WD, it does not do so into new shells, but instead merges the accreted material into existing shells.
> 
> This has the effect of artificially injecting small amounts of hydrogen below the WD-accretion envelope boundary, if the boundary is considered to be at a mass depth of 1.0000127678359980 M_sun, the original WD mass. This subsequently leads to the first hydrogen ignition occurring below the WD-Envelope boundary, which is not physically possible.
> 
> Therefore, I need MESA to accrete the solar material into new shells above the WD, or merge the material into the white dwarfs existing shells without artificially mixing the solar material and WD material in the process. From trying a few different mesh adjustment controls, I haven’t been able to achieve this so far, so I would be grateful for any insight anyone may have. I look forward your suggestions and thank you in advance!
> 
> 
> Best regards,
> Arman Aryaeipour
> 
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