[Mesa-users] Loss of angular moment

[Rob Farmer]

Hi
To use other_torque you need a rotating model, you need to set:

change_rotation_flag = .true.

in your star_job inlist to change the rotation flag, new_rotation_flag
only  changes the rotation flag if change_rotation_flag = .true.

The other issue is your using s% omega_avg_surf, but that gets set after
the other_torque call. When using the other_ routine the best bet is to
always "goto the source" of the stellar structure data, rather than any use
any shorthand variables as they may not be set. In this case you'll want to
look at the s% omega array which stores the rotation information for the
star. See set_surf_avg_rotation_info in star/private/star_utils.f90 for how
s% omega_avg_surf is implemented, you'll want to copy the relevant bits in
your run_star_extras file for computing the surface averaged value.

Rob


On 20 April 2018 at 14:18, Roque Caballero Navarro <rcaballeron at hotmail.com>
wrote:

> Hi Rob,
>
>    Please find attached the requested files.
>
> Kind regards,
>
> Roque
> ------------------------------
> *De:* Rob Farmer <r.j.farmer at uva.nl>
> *Enviado:* viernes, 20 de abril de 2018 12:12
> *Para:* Roque Caballero Navarro
> *Cc:* mesa-users at lists.mesastar.org
> *Asunto:* Re: [Mesa-users] Loss of angular moment
>
> Hi
>
> This is not enough information to help you. Please provide your inlists
> and run_star_extras.f
>
> Rob
>
> On 20 April 2018 at 12:06, Roque Caballero Navarro via Mesa-users <
> mesa-users at lists.mesastar.org> wrote:
>
> Dear all,
>
>    I'm trying to implement a magnetic braking routine based on Matteo
> Cantiello exercise propose during the Mesa school 2012 (here the details
> <http://cococubed.asu.edu/mesa_market/ewExternalFiles/2012_cantiello.zip>.)
> Well, for doing it I'm using the hook other_torque and the code is
> implemented, as usual, in the run_extras_star.f file. Below you can see the
> core part of the implementation:
>
>    1. *         if (s% use_other_torque) then*
>    2.
> 3.
> *            !Star data *
>    4.
> *            r_st = s% r(1) *
>    5.
> *            m_st = s% m(1) *
>    6.
> *            omega_surf = s% omega_avg_surf *
>    7.
> *            m_dot = s% star_mdot *
>    8.
> 9.
> *            v_esc = 618 * (((Rsun/r_st)*(m_st/Msun)))**0.5 *
>    10.
> 11.
> *            v_inf = 1.92 * v_esc *
>    12.
> 13.
> *            B = s% x_ctrl(6) *
>    14.
> 15.             *eta_surf = abs(((r_st/Rsun)**2/B**2)/(m_dot * v_inf))*
>    16.
> 17.
> *            j_dot = two_thirds * m_dot * omega_surf * (r_st/Rsun)**2 *
>    eta_surf *
>    18.
> 19. *            s% extra_jdot(1) = j_dot*
>    20. *            !s% extra_jdot(1) = -1*
>    21.
> 22.
> *            if (debug_use_other_torque) then *
>    23.
> *               write(*,*) "Rsun=", Rsun, "Msun=", Msun, "r_st=", r_st,
>    "m_st=", m_st, & *
>    24.
> *                  "v_esc=", v_esc, "v_inf", v_inf, "B", B, "m_dot",
>    m_dot, "eta_surf", eta_surf, & *
>    25.
> *                  "omega_surf", omega_surf, "j_dot", j_dot *
>    26.
> *            end if *
>    27.
> 28.
> *            s% x_ctrl(7) = v_esc *
>    29.
> *            s% x_ctrl(8) = v_inf *
>    30.
> *            s% x_ctrl(9) = eta_surf *
>    31.
> *            s% x_ctrl(10) = j_dot *
>    32.
> *            s% x_ctrl(11) = m_dot *
>    33.
> 34. *         end if*
>
> The input parameters for the calculation are the radius, mass, loss of
> mass and velocity at surface (lines 4 to 7). After some calculations, I end
> up with a loss of angular moment j_dot which I pass back using the array
> extra_jdot (line 20). After running a simulation with this routine
> activated, I'd expect to have lower values of velocity at surface but I
> couldn't find any difference. I've even assigned an unreal value (line 20)
> to the extra_jdot array but nothing changed. So, something must be wrong or
> missing in the implementation. As you maybe has already noticed, I'm just
> providing a value to one cell, the outermost  one. I'm assuming that only
> this layer is affected by the magnetic braking effect.
>
> As usual, any help is more than welcome.
>
> Kind regards,
>
> Roque
>
>
>
>
>
>
>
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