[mesa-users] Accretion with different entropy

[Bill Paxton]

Hi,

You might also try using a newer technique that I've added with surface entropy in mind.
It works to set the entropy at the surface cell indirectly by setting the pressure and temperature
that will produce the desired result.

         !### use_atm_PT_at_center_of_surface_cell
         
         ! The surface boundary conditions for pressure and temperature,
         ! compare the model values at the center of the surface cell to
         ! values derived from the P and T returned by the atm module.
         ! If this flag is true, then the atm values are directly used.
         ! If false, then the values from the atm are treated as being
         ! for the outer boundary of the surface cell, and those values
         ! are used to estimate corresponding values for the cell center
         ! for comparison to the model values at the cell center.
         
         ! Most cases will have this flag false.
         ! An example that sets this flag true is a case in which are 
         ! using a special boundary condition (BC) routine to force
         ! a certain entropy for the surface cell.  In that situation,
         ! it is better to have the special BC directly return P and T
         ! for the center of cell 1 to produce the desired entropy.

      use_atm_PT_at_center_of_surface_cell = .false.

In addition to your specified surface entropy, you need another thermodynamic
quantity such as temperature, pressure, or density.  
E.g., if it is T, then call the eos with entropy and T to find corresponding P.
Then return T and P as surface BCs -- that will give you
your desired entropy at the surface.
See eos/public/eos_lib.f90, eosDT_get_Rho for details.

Good luck,
Bill






On May 22, 2015, at 1:20 AM, Francis Timmes wrote:

> try these first
> 
> http://sourceforge.net/p/mesa/mailman/message/31007882/
> http://sourceforge.net/p/mesa/mailman/message/30562245/
> 
> fxt
> 
> 
> 
> 
>> On May 21, 2015, at 7:59 AM, efrats at physics.technion.ac.il wrote:
>> 
>> 
>> Dear all,
>> 
>> I would like to accrete mass onto a WD with a different entropy than  
>> the WD's surface.
>> Is there a flag that controls the entropy of the accreted material?
>> Also, what are the limitations on such accretion in MESA?
>> 
>> Best regards,
>> Efrat
>> 
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