[Mesa-users] taking very small steps during accretion

[harish sorrout]

Thankyou sir,

I have some query regarding the relax mass_ change .

1. When I will do relax mass_change over 100 yrs. Does white dwarf cool
during this years?
2. Does physical values of WD change or not?
3. What is the purpose of relax mass_change.



 I request you  Please clarify.

With regards

Harish Kumar


On Tue, 17 Aug, 2021, 07:56 Wolf, William M, <WOLFWM at uwec.edu> wrote:

> You can still do that. You just need to relax the value of mass_change
> over many time steps (which can be short) rather than turning it on
> instantaneously. Once the new value of mass_change is achieved, it can
> remain at the high value indefinitely. It’s the process of getting from one
> value of mass_change to another that requires the relaxation process.
>
> For instance, you might relax the value of mass_change slowly over 100
> years of evolution, and then leave it on at the new constant high rate for
> 100,000 more years of evolution.
>
> Regards,
>
> Bill Wolf
> ------------------------------
> *From:* harish sorrout <harishsorrout at gmail.com>
> *Sent:* Monday, August 16, 2021 8:11:01 PM
> *To:* Wolf, William M <WOLFWM at uwec.edu>
> *Cc:* Mesa-users <mesa-users at lists.mesastar.org>
> *Subject:* Re: [Mesa-users] taking very small steps during accretion
>
> Thanks for the tip!
> But sir I wanted to study long term evolution of steady buring of helium
> during accretion on to WD i.e accretion with fixed rate. Also some people
> have done this with such high accretion rates.
>
>
> On Tue, 17 Aug, 2021, 02:37 Wolf, William M, <WOLFWM at uwec.edu> wrote:
>
> Hi Harish,
>
>
>
> It looks like in your inlist, you have mass_change = 1.5d6. I advise that
> instead of just turning on the mass change full blast, you ramp it over
> time. In particular, I’d look at the relax_mass_change controls, which let
> you change the value of mass_change over time.
>
>
>
> However, with such a high accretion rate, you might have to do this in
> steps, as this control increases the accretion rate linearly. That is, if
> you ramp things up from 0 to 1.5d-6 over 100 timesteps, the very first
> timestep will abruptly turn on accretion at 1.5d-8 Msun/yr, which may also
> be too fast. Perhaps first adjust it to 1d-8, save a model, and then adjust
> it again to your final accretion rate. If the model you are loading was
> already accreting matter, you may be able to be more aggressive and do this
> in one relaxation.
>
>
>
> Good luck!
>
>
>
> Regards,
>
>
>
> Bill Wolf
>
>
>
> *From: *Mesa-users <mesa-users-bounces at lists.mesastar.org> on behalf of
> harish sorrout via Mesa-users <mesa-users at lists.mesastar.org>
> *Date: *Monday, August 16, 2021 at 6:09 AM
> *To: *Mesa-users <mesa-users at lists.mesastar.org>
> *Subject: *[Mesa-users] taking very small steps during accretion
>
> Respected sir,
>
>
>
> I am performing a simulation of long term evolution of WD accreting matter
> with accretion rate 1d-6 on my laptop with 4 threads and 16 GB ram. It is
> taking very small time steps and to increase time steps I have done many
> things like change mesh_coeff, var_control but I have failed to increase
> the time steps and I have run it more than 3-4 days. I wanted to achieve
> the Chandrasekhar limit of WD but it looks very different with this time
> step . because it will take 20 to 25 days to achieve ch mass limit. Here I
> am sharing an inlist file and TRHO plot.
>
>
>
> kindly help me where am i wrong. and how can i achieve the target.
>
>
>
> Thanking you
>
>
>
> with regards
>
> Harish kumar
>
> research scholar
>
>
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