[mesa-users] Limite convective velocities

[熊赫然]

Thanks for your advice, i will read the section and try the options. But i don't think the timescales are too large, as sometimes it was lesser than 1d-6 during the flash.

在2016-06-20 02:58:08，熊赫然xiongheran at ynao.ac.cn写道：



On Jun 19, 2016, at 11:21 AM, 熊赫然 wrote:

Hello every MESA users:
  I expect to limite convective velocities when the star surfer he flash. My MESA version is 7184.  I have tried the alter the option peak_burn_vconv_div_cs_limit = 1, but it seems to be uneffective to significant change the convective origon' spreading. Are there any other operations that i can do?





Note that the rate of spread of the convection zone is not the same thing as the convection velocity.


Which of those is your concern?   Is your concern that the newly created convection zone at the helium core flash spreads faster than you expect?


If so, then limiting convection velocities is unlikely to do what you want unless it reflects unphysical accelerations of convective material.


For that possiblity, see section 4.7 of the recent mesa instrument paper.   There are 2 options related to limiting convective accelerations:




            !### min_T_for_acceleration_limited_conv_velocity


            ! Acceleration limiting based on Wood 1974 and Arnett 1969.
            ! Wood, P.R., ApJ, 190:609-630, 1974. (Appendix V, eqns 1-3)
            ! Arnett, W.D., 1969, Ap. and Space Sci, 5, 180.


         min_T_for_acceleration_limited_conv_velocity = 99e9






            !### mlt_accel_g_theta


            ! use this (if > 0) for limiting the acceleration of convection velocities.


         mlt_accel_g_theta = -1




I'm not sure these are both in 7184 -- you'll need to check controls.defaults.


 
However I doubt is this is actually your problem since the timescales (and hence the timesteps) at the helium core flash are large enough that it is unlikely that there will be excessive accelerations.   




-b





















                                                                                                             &n bsp;                                                                  With kind regards
                                                                                                  ;                                                                               Heran Xiong








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