[mesa-users] Change Mesh Resolution Dynamically?

[Bill Paxton]

On Dec 14, 2014, at 4:47 PM, Spencer C Wallace wrote:

> Couple of questions about 'other_mesh_fcn_data':
> 
> 1. Do changes I make to the 'vals1' array trigger changes to the mesh during the current time step, or do I have to wait until the next time step to see the effects?

remesh is done early in the timestep.   try setting the 'trace_evolve' control true and look for mention of remesh.




> 
> 2. How exactly does the 'vals1' array affect the mesh? If I want to increase resolution between zones k and k+n in a model, do I set vals1(k:k+n) to some constant nonzero value, or is the change in 'vals1' between adjacent zones that actually triggers mesh refinement?


It it the magnitude of the change in mesh function values from zone to zone that controls mesh resolution.  That's the "delta" in "mesh_delta_coeff" -- it determines how large the delta can be before causing a split.

See section 5.4 in the 2nd mesa paper.



-Bill





> 
> Spencer Wallace
> 
> On Tue, Sep 9, 2014 at 1:10 PM, Bill Paxton <paxton at kitp.ucsb.edu> wrote:
> 
> On Sep 9, 2014, at 12:49 PM, Spencer C Wallace wrote:
> 
>> Thanks! I didn't realize I modify the inlist controls through the star pointer.
> 
> it is always an option to change inlist parameters from your run_star_extras routines.
> all of the &controls parameters are defined in the star_info structure, so s% xtra_coef_b_l_nb_czb = 0.5 has the same effect as setting it in the inlist.
> the &star_job controls are also accessible, but keep in mind that they are defined inside a substructure of star_info called "job".
> so from your code you'd write something like s% job% pgstar_flag = .true. 
> 
>> Is it safe to change the mesh tolerance parameters from 'other_mixing', or do you suggest writing a routine through 'other_mesh' to do it?
> 
> 
> The parameters will be used during the remesh, and that happens at the start of the step.
> 'other_mixing' is called after the remesh, so that's not what you want (at least not if you want the change to happen for the current step).
> by 'other_mesh' I assume you mean 'how_many_other_mesh_fcns' and 'other_mesh_fcn_data' -- they are called when 'use_other_mesh_functions' is true.   you could set the mesh parameters from either of those.
> 
> The easiest thing would be to set them in extras_finish_step so you don't need to use a hook -- they'll take effect with the next step.  
> 
> 
> Good luck,
> Bill
> 
> 
> 
> 
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