[Mesa-users] Loss of angular moment

[Rob Farmer]

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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