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Re: mesa-users] Manual Change of Accretion Composition
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From: Max K. <ka...@rp...> - 2010-07-02 18:42:01
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Bill, I was intentionally using the WD with the H/He stripped off to see if I could use a pure C/O white dwarf. At any rate, I tried accreting just helium onto the surface of the pure C/O WD to avoid the ignition problem, but I received the same result. I also received the same result by trying to do the same thing (accrete pure helium, as well as H/He) on a model with H/He remaining on the surface. Max Katz Rensselaer Polytechnic Institute Physics, Class of 2011 On Fri, Jul 2, 2010 at 2:30 PM, Bill Paxton <pa...@ki...> wrote: > Hi Max, > > Please try a different WD --- one that already has some H/He on the > surface. > Most of the ones in data/star_data/white_dwarf_models have some. > I artificially removed the outer H/He for the 1.000 Msun WD's, and that > might be the source of the problem you are seeing. > > -B > > > > > > > > On Jul 2, 2010, at 11:23 AM, Max Katz wrote: > > Bill, > > After playing around some more I realized a critical flaw - I did not > change one of the other necessary parameters, mass_change_full_off_dt - this > parameter gives the number of seconds below which mass change is > automatically turned off. Since it is initially set at 1d3, the code was > just going to a lower time-step where the mass change would be turned off. > To combat this, I decreased this to a very small number (like 1e-7) and also > changed min_timestep_limit to 1e-10 (the latter is also measured in > seconds). However, the code just kept on changing to a smaller time-step, > low enough that it could evade mass addition (at one point it was around > 10^-13 years). > > I also tried starting with accretion composition the same as the surface, > then after it was satisfied with the accretion, dropping the accretion rate > to a lower number and manually changing the composition. This, unfortunately > did not work either - as soon as I changed the composition, it went to very > low time-steps where mass change was zero. I'm open to other suggestions if > anyone has ideas on how to relax the mass change in. > > I also wanted to see if I could relax in the composition change - so I set > the following in the controls inlist - the idea was to accrete something of > similar, but not the same, composition, and then gradually increase the H/He > and decrease the C/O. However, when I do this the code returns an error and > crashes (*** glibc detected *** ./star: free(): invalid pointer: > 0x00007fdfcc000d50 ***). > > accretion_h1 = 0.01 ! mass fraction > accretion_h2 = 0. > accretion_he3 = 0. > accretion_he4 = 0.01 > accretion_zfracs = 0 > > z_fraction_li = 0. > z_fraction_be = 0. > z_fraction_b = 0. > z_fraction_c = 0.63 > z_fraction_n = 0. > z_fraction_o = 0.37 > z_fraction_f = 0. > z_fraction_ne = 0. > z_fraction_na = 0. > z_fraction_mg = 0. > z_fraction_al = 0. > z_fraction_si = 0. > z_fraction_p = 0. > z_fraction_s = 0. > z_fraction_cl = 0. > z_fraction_ar = 0. > z_fraction_k = 0. > z_fraction_ca = 0. > z_fraction_sc = 0. > z_fraction_ti = 0. > z_fraction_v = 0. > z_fraction_cr = 0. > z_fraction_mn = 0. > z_fraction_fe = 0. > z_fraction_co = 0. > z_fraction_ni = 0. > z_fraction_cu = 0. > z_fraction_zn = 0. > > Max Katz > Rensselaer Polytechnic Institute > Physics, Class of 2011 > > > On Fri, Jul 2, 2010 at 1:06 PM, Max Katz <ka...@rp...> wrote: > >> Bill, >> >> The simulation works just fine without accretion, and mass change without >> manual composition change works fine - it just accretes C and O (I noticed >> that after a while something started happening where the timestep got really >> small, but I didn't wait around long enough to see what happened). >> >> I tried your suggestion, both at your suggested settings and even smaller >> ones, and the same result occurred. I set max_backups_in_a_row to 50, and I >> noticed that after a number of retries, it eventually gives up on mass >> change and continues without it (lg Mdot is -99 on the pgplot screen); I >> even stopped it, increased the mass_change rate and restarted, and it >> continued on with zero mass change, without any backups or retries. >> >> - Max >> >> >> On Fri, Jul 2, 2010 at 12:08 PM, Bill Paxton <pa...@ki...>wrote: >> >>> >>> >>> Hi Max, >>> >>> The change in accretion composition should be fine. Perhaps the problem >>> is the abrupt start of accretion at the 5d-9 rate. >>> >>> Let's separate the 2. What happens if you do the 5d-9 mass change >>> without changing the accretion composition? >>> >>> Also, you should try manually turning up the accretion rate while keeping >>> the timestep small. >>> >>> Try something like max_years_for_timestep = 1d-7 to start with, and >>> mass_change = 1d-12 -- or whatever it >>> takes to get things to converge. (BTW: I'm assuming that everything >>> works without accretion turned on, right?) >>> Let things run for a while until it is happy (i.e., running at max >>> allowed timestep). Then start increasing the >>> mass_change -- at each increment, let it run until it is happy, then >>> increase again. Once you reach the >>> desired accretion rate, remove the limit on max_years_for_timestep. >>> >>> This is a crude manual version of what the various "relax" operations do. >>> And if you feel ambitious, you can >>> write your own relax routine to do "relax_to_mass_change". >>> >>> Let me know how it goes. >>> >>> -Bill >>> >>> >>> >>> >>> >>> On Jul 2, 2010, at 6:46 AM, Max Katz wrote: >>> >>> > Hello, >>> > >>> > In an attempt to create my own nova, I used the model 1.000_Tc_3e7.mod >>> in mesa/data/star_data/white_dwarf_models. This is a pure C/O white dwarf of >>> 1 solar mass. The goal is to get it to go nova, so I set an accretion rate >>> of 5 x 10^-9 (units are solar masses per year). However, the default >>> behavior for accretion is to use the same composition for the accreted >>> matter as there is on the surface. Since adding C and O to the surface >>> wouldn't yield the nova I was looking for, I set the following in the >>> controls namelist: >>> > >>> > mass_change = 5d-9 >>> > accrete_same_as_surface = .false. >>> > accretion_h1 = 0.75 >>> > accretion_h2 = 0. >>> > accretion_he3 = 0. >>> > accretion_he4 = 0.25 >>> > >>> > However, when I try to run with these settings on, the run cites >>> "adjust_mass_failed", and crashes after hitting the default max number of >>> backups (15). I tried the same settings on a different case and got the same >>> error. If anyone has experience with changing the accretion composition, I >>> would appreciate it if you could give some insight as to what I might be >>> doing wrong. Thanks. >>> > >>> > Max Katz >>> > Rensselaer Polytechnic Institute >>> > Physics, Class of 2011 >>> > >>> ------------------------------------------------------------------------------ >>> > This SF.net email is sponsored by Sprint >>> > What will you do first with EVO, the first 4G phone? >>> > Visit sprint.com/first -- >>> http://p.sf.net/sfu/sprint-com-first_______________________________________________ >>> > mesa-users mailing list >>> > mes...@li... >>> > https://lists.sourceforge.net/lists/listinfo/mesa-users >>> >>> >> > > |
