I think Jeff's interpretation is correct.  The dark matter particles are too massive with respect to the mass of the gas in the grid cells.  Since the force resolution of the gravity solver on the root grid is 2 *dx, it makes sense to run with twice the number of grid cells as particles in one direction, but I don't think increasing that ratio any higher is a good idea.

Britton

On Wed, Feb 9, 2011 at 2:06 PM, j s oishi <jsoishi@gmail.com> wrote:
Hi Shankar,

I'm not an expert on large scale structure, but this looks completely
correct to me in the sense that yt and enzo appear to be doing just
what you would expect. if you increase the grid resolution without
increasing the number of dark matter particles, eventually you will
reach a point where individual dark matter particles will accrete gas.
If you want to increase grid resolution without a concomitant increase
in particle number, you may need to re think your initial conditions.

At any rate, I don't think this is a yt issue.

thanks,

jeff

On Wed, Feb 9, 2011 at 10:48 AM, Agarwal, Shankar <sagarwal@ku.edu> wrote:
> Hi,
>
> I have made gas density projections (attached) for two identical simulations, except than one was run with GriDims=512 while the second was run with GridDims=1024. The BoxSize=200 Mpc/h and ParticleDims=256 for both.
>
> Can anyone tell me why does the 1024grid.png look a lot grainier than the 512grid.png ? Is it something to do with this command...
>
>  p = pc.add_slice("Density", ax)
>
> I guess the slice is too thin for 1024, so I can't really compare the 2 plots. Let me know.
>
>
> Sorry to have attached 2 huge files. Are there other ways?
>
> Shankar
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>
>
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