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

[Francis Timmes]

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
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