[Mesa-users] Too small timestep

[Rob Farmer]

Hi,

The terminal output should tell you what is limiting the timestep for your
model, have a look back over the output from around when the model started
having difficulties.  Have a look at the information here
http://mesa.sourceforge.net/controls_defaults.html#timestep_controls for
how to intercept the timestep controls for each star as well as
http://mesa.sourceforge.net/binary_controls_defaults.html#timestep_controls
for the binary controls.

Rob

On Tue, 21 Apr 2020 at 11:34, Jelena Petrović <jpetrovic at aob.rs> wrote:

> Dear all,
>
> I am running a massive binary model (initially 56+33 Ms without
> rotation) and I have a following problem:
>
> The primary is in helium core burning stage (about 30% left), there is
> no mass transfer anymore, but the timestep does not increase above about
> 10^(-3.5).
> So, the model is running, but takes far too long..is there something I
> can do to speed this up?
> I have also noticed that this significant decrease of timestep also
> happens for single stars more massive than 75-80 Ms towards the end of
> core helium burning.
>
> I am copying a part of output from binary model under for extra info.
>
> Many thanks!
> Jelena
>
>
> __________________________________________________________________________________________________________________________________________________
>
>         step    lg_Tcntr    Teff       lg_LH     lg_Lnuc     Mass
> H_rich     H_cntr     N_cntr     Y_surf     X_avg     eta_cntr  zones
> retry
>     lg_dt_yr    lg_Dcntr    lg_R       lg_L3a    lg_Lneu     lg_Mdot
> He_core    He_cntr    O_cntr     Z_surf     Y_avg     gam_cntr  iters
> bckup
>       age_yr    lg_Pcntr    lg_L       lg_LZ     lg_Psurf    lg_Dsurf
> C_core     C_cntr     Ne_cntr    Z_cntr     Z_avg     v_div_cs
> dt_limit
>
> __________________________________________________________________________________________________________________________________________________
>
>      3291860   8.345682  7.294E+04   3.151650   5.603874  15.807769
> 0.521665   0.000000   0.000000   0.842355   0.003096  -4.578180   1238
> 369241
>    -3.447671   2.763773   0.590847   5.374911   2.335906  -4.774538
> 15.286104   0.295960   0.213693   0.019418   0.414412   0.066374      3
>    310
>   4.0589E+06  19.107291   5.587066   5.212633   4.893538  -8.903023
> 0.000000   0.466210   0.020045  7.040E-01  5.825E-01  0.426E-01  max
> increase
>
>
>
> __________________________________________________________________________________________________________________________________________________
>
>         step    lg_Tcntr    Teff       lg_LH     lg_Lnuc     Mass
> H_rich     H_cntr     N_cntr     Y_surf     X_avg     eta_cntr  zones
> retry
>     lg_dt_yr    lg_Dcntr    lg_R       lg_L3a    lg_Lneu     lg_Mdot
> He_core    He_cntr    O_cntr     Z_surf     Y_avg     gam_cntr  iters
> bckup
>       age_yr    lg_Pcntr    lg_L       lg_LZ     lg_Psurf    lg_Dsurf
> C_core     C_cntr     Ne_cntr    Z_cntr     Z_avg     v_div_cs
> dt_limit
>
> __________________________________________________________________________________________________________________________________________________
>
>    2 3291860   7.600318  4.336E+04   5.415654   5.415654  33.261330
> 33.261330   0.401824   0.011361   0.790213   0.480099  -6.888723   1036
> 369241
>    -3.447671   0.472190   0.956559 -24.750403   4.249309 -99.000000
> 0.000000   0.578563   0.001896   0.019419   0.500184   0.010993      2
>   310
>   4.0589E+06  16.268422   5.414956 -10.058929   4.087307  -9.021085
> 0.000000   0.000166   0.002099  1.961E-02  1.972E-02  0.951E-09  max
> increase
>
>
>
> __________________________________________________________________________________________________________________________________________________
>
> binary_step      M1+M2      separ       Porb          e      M2/M1
> pm_i    donor_i    dot_Mmt        eff       Jorb      dot_J    dot_Jmb
>        lg_dt         M1         R1         P1      dot_e      vorb1
>   RL1    Rl_gap1     dot_M1   dot_Medd      spin1    dot_Jgr    dot_Jls
>       age_yr         M2         R2         P2       Eorb      vorb2
>   RL2    Rl_gap2     dot_M2      L_acc      spin2    dot_Jml  rlo_iters
>
> __________________________________________________________________________________________________________________________________________________
>
> bin 3291860  49.069099  66.747222   9.021226  0.000E+00   2.104113
>     0          1  0.000E+00  0.000E+00  3.708E+54 -8.467E+40  0.000E+00
>    -3.447671  15.807769   3.898042   0.000000  0.000E+00 253.841150
> 21.139329 -8.156E-01 -1.681E-05  1.000E+99  0.000E+00 -1.270E+35
> 0.000E+00
>   1.3608E+01  33.261330   9.048141   0.000000 -1.495E+49 120.640466
> 29.670694 -6.950E-01  0.000E+00  0.000E+00  0.000E+00 -8.467E+40
>   1
>
>
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>
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