[Users] Achieve Cell-Center in NR simulation

Bernard Kelly physicsbeany at gmail.com
Sun Jun 23 07:49:11 CDT 2019

Hi Steve.

It looks like the "avoid_origin" options are commented out in your
parameter file, so they wouldn't be active. However, since they're
part of the ReflectionSymmetry thorn, they'd only work if you were
using reflection symmetry in one of more of the spatial dimensions.

To get what you want to happen, I'd manually shift the CoordBase
parameters a bit:

xmin -> xmin + delta
ymin -> ymin + delta
zmin -> zmin + delta
xmax -> xmax + delta
ymax -> ymax + delta
zmax -> zmax + delta

... where "delta" is half of your *finest* grid spacing --- 1/64, if
I'm reading the parameter file correctly. Then all the grids (base
level 0 and Carpet's refined levels 1-4) will be centered slightly off
the origin, as you wanted.


On Sun, 23 Jun 2019 at 04:10, Steve Hawk <steve-hawk1998 at outlook.com> wrote:
> Hello:
> Thanks for giving some hints about adaptive mesh refinement with the help of Roland, but I feel sorry that I came across some new problems about cell-centering when I try to simulate "the transition from wormholes to trumpets” considering Schwartzchild metric.
> Since the singularity (0,0,0) exists under the metric of Schwartzchild, I want to make use of cell-centered method to avoid the singularity. Although there is an option CartGrid3D::avoid_origin = “yes” in the thorn CartGrid3D, it seems that it doesn’t works properly: the data related to the grid points (0,0,0) is still been calculated (very large!). The related par file is attached in the attachment.
> So I am wondering is there a method to solve the problem or any parameters of thorns governing the cell-centering methods?
> Thanks!
> Best Regards!
> Xiaoxiao
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Bernard Kelly -- CRESST Assistant Research Scientist, NASA/GSFC
Gravitational Astrophysics Laboratory --- Code 663

Phone: +1 (301) 286-7243 *** Fax: +1 (301) 286-2226
Web: http://science.gsfc.nasa.gov/sed/bio/bernard.j.kelly
ORCID: orcid.org/0000-0002-3326-4454

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