[Mesa-users] relaxing entropy

[Akaash Conhye]

Hi all,

I've been trying to relax a white dwarf's entropy profile (obtained from hydrodynamic simulations). The template I used was wd_cool_0.6M. To the file inlist_wd_cool_0.6M I've added the following lines:

      relax_initial_entropy = .true.
      max_steps_to_relax_entropy = 1000
      timescale_for_relax_entropy = 1d-9 ! in years
      max_dt_for_relax_entropy = 1d-8 ! in years
      num_timescales_for_relax_entropy = 100
      relax_entropy_filename = 'entropy_unrlx.dat'

Where entropy_unrlx.dat is my entropy profile. Upon running, here is the output on my terminal:

read inlist_wd_cool_0.6M
 set_eos_PC_parameters
                             mass_fraction_limit_for_PC    1.0000000000000000D-03
                                       logRho1_PC_limit    2.9990000000000001D+00
                                       logRho2_PC_limit    2.7999999999999998D+00
                                     log_Gamma_all_HELM    1.0000000000000000D+00
                                       log_Gamma_all_PC    1.3010299956000000D+00
                                 PC_Gamma_start_crystal    1.7400000000000000D+02
                                  PC_Gamma_full_crystal    1.7600000000000000D+02
                                               PC_min_Z    9.9900000000000000D-01
load saved model wd_0.6.mod

                    WARNING -- inlist initial_z ignored    1.0000000000000000D-02
                          using saved initial_z instead    2.0000000000000000D-02


                                  relax_initial_entropy
 relax_entropy: max_steps_to_use        1000
 retry     129
 retry     129
backup     129
 retry     129
 retry     129
backup     129
 retry     129
 retry     129
                                                    dt    7.7046264609375010D-11
                                     min_timestep_limit    1.0000000000000001D-09

 stopping because of problems dt < min_timestep_limit

 do_relax_initial_entropy ierr          -1
 do_star_job_controls_after ierr          -1
 before_evolve_loop ierr          -1
DATE: 2020-09-08
TIME: 11:00:31

Some things Ive tried to do to fix this problem:

  1.   decreasing min_timestep_limit (by setting it to a smaller value in the controls section of my inlist) so that i don't get the inequality dt<min_timestep_limit. But this doesn't solve the problem as dt continues to get smaller.
  2.  using a different entropy profile. Initially I'd thought that there was something wrong with my entropy profile, so I tried using the one provided in the "relax_composition_j_entropy" template to see what would happen. I got the same error message.

the version of MESA im using is 12115. My operating system is Ubuntu 20.04.1 LTS 64 bit. Im running MESA on a cluster (eureka).

Thanks,

Akaash
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