[mesa-users] Fixed rate accretion onto WD with full structure

[Robert FARMER]

Hi
Plots could be useful to see whats going on at the surface, burning?
mixing? nothing?

Also, i also see your using accrete_same_as_surface=.true. to accrete the
same compostion of material as the surface of your WD? which implies your
stripping material from one WD onto another?

Maybe using
 accrete_same_as_surface = .false.
accrete_given_mass_fractions = .true.

and setting a different compsotion (Say H or H/He) will help?

Rob


On Wed, May 20, 2015 at 10:08 AM, Manos Chatzopoulos <
manolis at flash.uchicago.edu> wrote:

>  Hi Robert,
>
> At the time the timestep goes down I see the string "neg_mass_frac"
> appearing and then I set the
> neg_mass_fraction_hold = 10 flag to a variety of values without success.
>
> Thanks,
>
> Manos
>
>
> On 5/20/15 11:59 AM, Robert FARMER wrote:
>
>  Hi
>  If you look at your terminal output you should see a string at the end of
> the parameters in the dt_limits section. This string is telling you why
> mesa is limiting the timestep. Then you can look that string up in the
> controls.defaults file which  will tell you what parameter you can chnage
> to make mesa less sensistive to that control and thus take a larger
> timestep.
>
>  Rob
>
> On Wed, May 20, 2015 at 8:55 AM, Manos Chatzopoulos <
> manolis at flash.uchicago.edu> wrote:
>
>> Dear all,
>>
>>  I am setting up a relatively simple MESA problem where I want to accrete
>> mass at a constant rate (1d-9 Msun/yr) onto a white dwarf. I know there are
>> numerous binary test_suite problems that deal with accretion onto a WD as a
>> point mass, but in my case I want to include the full
>> structure of the WD in the calculation because I want to see how several
>> parameters change (including angular momentum profile) as mass
>> is accreted. The problem I am dealing with is that the time-step becomes
>> tiny after a few time-steps not allowing me to complete a full
>> simulation for ~ 1bn years. That only happens when I accrete mass onto
>> the WD at a rate higher than ~ 1d-14 Msun/year. I need to use
>> a rate of 1d-9 Msun/year, however. I am using the "final.mod" WD profiles
>> from the test_suite problem agb_to_wd and wd_cool to start
>> the calculation. An example model and inlist (and profiles_columns.list)
>> are attached. I am using the latest version of MESA (7503).
>>  Any help on this would be appreciated. Thank you very much for your time!
>>
>> Best,
>>
>> Manos
>>
>> --
>> Dr. Emmanouil Chatzopoulos
>> Enrico Fermi Postdoctoral Fellow
>> Department of Astronomy & Astrophysics
>> FLASH Center for Computational Science
>> University of Chicago
>> https://www.linkedin.com/pub/manos-chatzopoulos/a1/688/a03
>> https://astro.uchicago.edu/people/manos-chatzopoulos.php
>>
>>
>>
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>
> --
> Dr. Emmanouil Chatzopoulos
> Enrico Fermi Postdoctoral Fellow
> Department of Astronomy & Astrophysics
> FLASH Center for Computational Science
> University of Chicagohttps://www.linkedin.com/pub/manos-chatzopoulos/a1/688/a03https://astro.uchicago.edu/people/manos-chatzopoulos.php
>
>
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