[FLASH-USERS] zoom-out simulations

[Slavin, Jonathan]

Hi Sean,

Yes sounds like what I'm after. I'll have to look into how to use those for
my case. If I were to use the time one, would it de-resolve the highly
resolved regions after the given time is reached?

Jon

On Thu, May 30, 2019 at 10:28 AM Sean M. Couch <couch at pa.msu.edu> wrote:

> Hi Jon,
>
> Depending on what exactly you are looking to do, it might already be
> possible with FLASH. FLASH4 already has the capability to reduce the
> maximum allowed refinement level as a function of radius. See the runtime
> parameter `gr_lrefineMaxRedDoByLogR` and `gr_lrefineMaxRedRadiusFact`. The
> latter is a bit arcane, but essentially sets the “angular” resolution of
> the resulting grid. But the value chose depends on the number of zones per
> block (`nxb`) since the resolution limiting is actually based on the
> _block_ size, not the _zone_ size directly.
>
> The second already-implemented feature that could be of use here is the
> runtime param `gr_lrefineMaxRedDoByTime`. This, if True, decreases the
> maximum allowed refinement level anywhere on the grid as a function of
> time. The behavior is set by the params `gr_lrefineMaxRedLogBase`,
> `gr_lrefineMaxRedTRef`, and `gr_lrefineMaxRedTimeScale`. See appropriate
> documentation online or the code directly. Combined with `gr_lrefineMaxRedDoByLogR`,
> this means you can “de-resolve” the inner region of your grid as the
> feature you are interested in moves out in radius. This nets you not only a
> reduction in the total number of zones in the simulation but, usually, a
> nice increase in the time step size. We have been using these features, in
> various combinations, for years in our supernova simulations.
>
> This all assumes that you are included the “large” scale region from the
> very start of your simulation. If you want to map an already-run simulation
> into a larger domain, literally zooming out, that’s harder. I did it a long
> time ago (with FLASH v2!) when I was a grad student but that code and
> capability are now part of the geological record, I fear.
>
> Sean
>
>
> ----------------------------------------------------------------------
> Sean M. Couch, Ph.D.
> Assistant Professor
> Department of Physics and Astronomy
> Department of Computational Mathematics, Science, and Engineering
> Facility for Rare Isotope Beams
> Michigan State University
> 567 Wilson Rd, 3250 BPS
> East Lansing, MI 48824
> (517) 884-5035 --- couch at pa.msu.edu --- www.pa.msu.edu/~couch
> On May 29, 2019, 1:45 PM -0400, Slavin, Jonathan <jslavin at cfa.harvard.edu>,
> wrote:
>
> Hi all,
>
> Often simulators will use zoom-in simulations - taking a part of a large
> simulation to focus on a small region of interest. I would like to do the
> opposite. I would like to take a fairly small scale simulation and embed it
> in a larger smooth background and reduce the refinement by a level or two.
> I imagine that this will require some significant coding, but I was
> wondering if anyone had tried something like this or could offer
> suggestions on how to do it. Thanks in advance for any help.
>
> Regards,
> Jon
>
> --
> Jonathan D. Slavin
> Astrophysicist - High Energy Astrophysics Division
> Center for Astrophysics | Harvard & Smithsonian
> Office: (617) 496-7981 | Cell: (781) 363-0035
> 60 Garden Street | MS 83 | Cambridge, MA 02138
>
>
>

-- 
Jonathan D. Slavin
Astrophysicist - High Energy Astrophysics Division
Center for Astrophysics | Harvard & Smithsonian
Office: (617) 496-7981 | Cell: (781) 363-0035
60 Garden Street | MS 83 | Cambridge, MA 02138
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