[Mesa-users] Difference between "setting" and "relaxing" rotation

[Nicholas J Nelson]

Okay, this has led to a follow-up question -- we're now using relax_surface_rotation_v to get a ZAMS model with a specified surface rotational velocity. If we use the default number of relaxation steps (100) we get a "rel_E_err" error after the relaxation has finished and evolution begins. If we decrease the number of relaxation steps to 25 that goes away. Is there something else we should be changing along with num_steps_to_relax_rotation?

The inlist we're using is attached.

Thanks,
Nick


Nicholas J. Nelson

Assistant Professor of Physics

Faculty Adviser, Society of Physics Students

California State University, Chico

njnelson at csuchico.edu

________________________________
From: Nicholas J Nelson <njnelson at csuchico.edu>
Sent: Wednesday, July 17, 2019 2:26 PM
To: Francis Timmes <fxt44 at mac.com>
Cc: mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Difference between "setting" and "relaxing" rotation

Thanks, Frank and Pablo. I figured someone (or some-two) would have a quick answer for that.


Nicholas J. Nelson

Assistant Professor of Physics

Faculty Adviser, Society of Physics Students

California State University, Chico

njnelson at csuchico.edu

________________________________
From: Francis Timmes <fxt44 at mac.com>
Sent: Wednesday, July 17, 2019 1:45 PM
To: Nicholas J Nelson <njnelson at csuchico.edu>
Cc: Frank Timmes <fxt44 at mac.com>; mesa-users at lists.mesastar.org <mesa-users at lists.mesastar.org>
Subject: Re: [Mesa-users] Difference between "setting" and "relaxing" rotation

some modifications are best done gradually over several steps in a pseudo evolution mode.
these operations have “relax” in their names.

many of these operations have an alternative, with “set” in name, that make the desired change all at once.
the “set” version is fine if a model can converge the modifications, but for larger changes where
that’s not possible, one will want to use “relax” instead.

here is an example. say i have a white dwarf and i want to modify the interior composition.
if i try to "set" a large composition change, the model will not converge.
if instead i "relax" the composition, the model will usually proceed just fine.

clearer?

fxt





> On Jul 17, 2019, at 1:32 PM, Nicholas J Nelson via Mesa-users <mesa-users at lists.mesastar.org> wrote:
>
> I'm working on a project that is looking at the effects of rotation on main sequence evolution and I've run into a question I can't seem to answer from the documentation. There appear to be two ways to activate rotation in Mesa -- namely one can use the group of inputs that begin with 'set' (e.g., set_omega, set_omega_step_limit) or one can use another group of inputs that begin with 'relax' (e.g., relax_omega, num_steps_to_relax_rotation). What is the difference between setting and relaxing?
>
> Thanks,
> Nick
>
> Nicholas J. Nelson
> Assistant Professor of Physics
> Faculty Adviser, Society of Physics Students
> California State University, Chico
> njnelson at csuchico.edu
> _______________________________________________
> mesa-users at lists.mesastar.org
> https://lists.mesastar.org/mailman/listinfo/mesa-users

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