[FLASH-USERS] 2D Spherical and Cartesian Geometry
Klaus Weide
klaus at flash.uchicago.edu
Fri Sep 23 09:49:27 EDT 2016
On Fri, 23 Sep 2016, Mordecai-Mark Mac Low wrote:
> Dear Michiel,
>
> On your second question: are you sure that you’re not setting up a
> cylindrical blast wave, rather than a spherical one? A 2D, slab
> symmetric, point explosion is effectively that of an infinite line
> charge, rather than a spherical, point explosion. The line charge
> indeed expands faster. There is, of course, an exact analytic solution
> for this. For an analogous case with a constant energy input, see eqs.
> 5-7 of Mac Low, McCray, & Norman, ApJ (1989). Therefore, you may be fine
> sticking with your Cartesian grid, so perhaps you don’t need to solve
> your first problem.
Yes indeed, to the above.
There is also a subsection in the FLASH Users Guide with some discussion
related to the meaning of 2D simulations, which might be useful to some:
8.11 Grid Geometry
8.11.1 Understanding Curvilinear Coordinates
Michiel, you may also want to refer to the provided SodSpherical example.
1) Note that Y ranges only from 0 to 90 degrees, with reflecting
boundaries in Y direction.
2) Note that the *physical* geometry set up in the SodSpherical problem
is cylindrical - comparable to a line charge - but the coordinates used by
FLASH are spherical, thus in the parfile:
# Grid geometry
geometry = "spherical"
Klaus
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