[mesa-users] overshooting

[umberto.battino at unibas.ch]

Dear Bill,

thanks so much for your help! I'll think upon that, it will surely be  
very useful.. :)
Cheers,

  Umberto

Quoting Bill Paxton <paxton at kitp.ucsb.edu>:

> Hi Umberto,
>
> Thanks for your question -- I think this is a case where we should
> use grep to track down the truth in the code in star/private.
> But first let me say that these parameters allow you to set "standard"
> values for the overshoot f parameters (such as appropriate for a 2 Msun star)
> and have them automatically reduced for lower mass stars.  The automatic
> reduction takes effect over a mass range that you specify using the
> controls mass_for_overshoot_full_on and mass_for_overshoot_full_off.
> You might check with Falk Herwig for the physical motivation for this.
> For the code details, grep will tell us where to look.
>
> /Users/bpaxton/mesa/star/private: grep mass_for_overshoot_full_on *
> ctrls_io.f:         mass_for_overshoot_full_on, &
> ctrls_io.f:         s% mass_for_overshoot_full_on =  
> mass_for_overshoot_full_on
> overshoot.f:            if (s% star_mass <= s%  
> mass_for_overshoot_full_on) then
> overshoot.f:                      (s% mass_for_overshoot_full_on -  
> s% mass_for_overshoot_full_off)
>
> The references in ctrls_io are defining the names for the &controls  
> inlist, so that's not what we want.
> We'll want to check the code in overshoot.f -- here's the relevant  
> section from the add_overshooting routine:
>
>          do i=1, n_conv_bdy ! from center to surface
>
>             if (s% conv_bdy_q(i) < s% min_overshoot_q) then
>                if (dbg) write(*,*) 'skip since s% conv_bdy_q(i) <  
> min_overshoot_q', i
>                cycle
>             end if
>
>             call set_f(i)
>
>             have_h1_czb = .false.
>
>             if (f_above == 0 .and. f_below == 0) cycle
>             if (s% star_mass <= s% mass_for_overshoot_full_off) cycle
>             if (s% star_mass <= s% mass_for_overshoot_full_on) then
>                frac = (s% star_mass - s% mass_for_overshoot_full_off) / &
>                       (s% mass_for_overshoot_full_on - s%  
> mass_for_overshoot_full_off)
>                frac = 0.5d0*(1 - cos(pi*frac))
>                if (dbg) write(*,1) 'overshoot frac', frac
>                f_above = f_above*frac
>                f_below = f_below*frac
>             end if
>
> We are looping over the convective boundaries deciding whether or  
> not to add overshooting.
> The test of min_overshoot_q prevents adding overshooting very near  
> the center.
> The call on set_f sets the f_above and f_below values depending on  
> what kind of convective zone it it.
> If star_mass is <= mass_for_overshoot_full_on, then we cycle to the  
> next boundary without adding overshooting.
> If star_mass is > mass_for_overshoot_full_off but less than  
> mass_for_overshoot_full_off, then the values
> of f_above and f_below are reduced by a value that depends on where  
> the star_mass lies in the range.
>
> Good luck,
> Bill
>
>
>
>
>
>
>
> On Dec 1, 2011, at 2:34 AM, umberto.battino at unibas.ch wrote:
>
>> Hi all,
>> I'm performing some tests varying overshooting.. I saw in
>> star_defaults.dek that  overshoot_f0_above/below parameter has to be
>> set.. moreover I saw that a range of star masses over which
>> overshooting is gradually enabled has to be set as well.. more
>> precisely the two parameters mass_for_overshoot_full_on and
>> mass_for_overshoot_full_off.. but what do they mean? Do they define a
>> mass range such as overshooting starts from
>> mass_for_overshoot_full_off and reaches its plenty efficiency at
>> mass_for_overshoot_full_on and major masses? Can anybody clarify this
>> point? :)
>> All the best,
>>
>>  Umberto
>>
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>



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