[mesa-users] Rapidly accreting metal-free protostars

[Bill Paxton]

On Apr 22, 2014, at 12:25 AM, Warrick Ball wrote:

> The second profile is dq as a function of the mass co-ordinate (in Msun).  To me, it looks pretty flaky in the interior.  Is this symptomatic, causal, or expected?  We haven't played with things like the mesh-spacing function or re-meshing criteria, so I guess that those may yet help.


Hi,

The relative mass, dq, of the cells is allowed to vary from neighbor to neighbor by a ratio given by this:
      
      mesh_max_allowed_ratio = 2.5 ! must be >= 2.5
         ! max ratio for mass of adjacent cells
         ! if have ratio exceeding this, split the larger cell 

We need to allow that much variation to avoid massive amounts of remeshing on each step -- partly because it is computationally expensive and (more importantly) remeshing introduces numerical diffusion that can blur the model.

We don't want the variation to be much larger or it can hurt convergence.    The default of 2.5 seems to work well.   I don't think it is the variation in dq that's causing your problems.    But you might need to use a finer mesh.

-B


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