[mesa-users] Hydrodynamic BCs

Bill Paxton paxton at kitp.ucsb.edu
Thu Apr 28 19:47:58 EDT 2016


On Apr 28, 2016, at 3:24 PM, Kenny Van wrote:

> Hi everybody,
> 
> With the new MESA update, 8118, I was unable to find a "use_hydrodynamic_surface_BCs". I was wondering if by default is this the boundary condition used?

Hi,

There were some new options for surface BC's added in 8118, so I dropped that old name that might be interpreted to mean there is a single "best" choice.

You should look through the new version of controls_defaults to see what's there.   If you read the comments in the old (7624) version, it will be clear what to use.

hint: here are the comments in 7624
         !### use_hydrodynamic_surface_BCs
         
         ! 1) gradient of compression vanishes at surface
            ! see Grott, Chernigovski, Glatzel, 2005.
            ! d_dm(d_dm(r^2*v)) = 0 at surface
            ! by continuity, this is d_dm(d_dt(1/rho)) = 0 at surface
            ! finite volume form is
            ! (1/rho(1) - 1/rho_start(1)) = (1/rho(2) - 1/rho_start(2))
            ! this BC determines the density for surface cell.
         
         ! 2) black body radiation at surface
            ! L = 4*pi*R^2*boltz_sig*T^4
            ! this BC determines the temperature for the surface cell given R and L.


look for similar comments in the new controls_defaults to get your answer.

Bill







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