[Mesa-users] Surface rotation velocity, num_steps_to_relax_rotation

[Anuj Gautam]

Dear MESA devs and users,

I am trying to evolve tracks for uniformly rotating intermediate mass (1.3-2 MSun) stars using MESA version r22.11.1.
I initiate rotation at age = 0, with surface velocities (new_surface_rotation_v, call it V_init) in the range 0 to 20 km/s. I am observing a "jump" in how the surface velocity evolves with age after a particular V_init. This V_init "jump point" varies with the stellar mass and metallicity.

Please see the attached plot of surf_avg_v_rot vs. age for a test star of 1.4 MSun and initial_z = 0.008. Please also see the corresponding inlist attached. (Kindly ignore the haphazard formatting, I am writing the inlists with a python automator so all added parameters are dumped at the end of each section.)

To initiate rotation, I add the following to the inlist:

change_rotation_flag = .true.
new_rotation_flag = .true.
change_initial_rotation_flag = .true.
set_initial_surface_rotation_v = .true.
set_surface_rotation_v = .true.
new_surface_rotation_v = V_init
relax_initial_surface_rotation_v = .true.
num_steps_to_relax_rotation = 100
set_uniform_am_nu_non_rot = .true.

If I instead do num_steps_to_relax_rotation<10, I do not see this "jump" in surf_avg_v_rot. What could be happening here? Or am I doing something wrong?
What exactly is the purpose of num_steps_to_relax_rotation? It is talked about very briefly in the docs...

Any and all help is appreciated.

Kind regards,
Anuj

__________________________________________________________________

This email (including any attached files) is confidential and is 

for the intended recipient(s) only. If you received this email by 

mistake, please, as a courtesy, tell the sender, then delete this 

email.

The views and opinions are the originator's and do not necessarily 

reflect those of the University of Southern Queensland. Although 

all reasonable precautions were taken to ensure that this email 

contained no viruses at the time it was sent we accept no 

liability for any losses arising from its receipt.

The University of Southern Queensland is a registered provider 

of education with the Australian Government.

(CRICOS Institution Code QLD 00244B / NSW 02225M, TEQSA PRV12081)
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20230411/97eec2c3/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: inlist_project_PreMS
Type: application/octet-stream
Size: 4518 bytes
Desc: inlist_project_PreMS
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20230411/97eec2c3/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: V_surf_jump.png
Type: image/png
Size: 83090 bytes
Desc: V_surf_jump.png
URL: <https://lists.mesastar.org/pipermail/mesa-users/attachments/20230411/97eec2c3/attachment.png>