[yt-users] Trouble projecting a derived field

Andrew Myers atmyers at berkeley.edu
Tue Sep 6 23:43:20 PDT 2011


Hi Nathan,

This is just a guess, but do you really mean to be taking the square root of
R cross V, at line 30? That quantity could potentially be negative,
depending on the sense in which the fluid is spinning.

-Andrew Myers


On Tue, Sep 6, 2011 at 5:54 PM, Nathan Goldbaum <goldbaum at ucolick.org>wrote:

> Hello all,
>
> Right now I'm trying to generate maps of the Toomre Q in an isolated galaxy
> simulation.  To do so, I'm using yt to generate maps of the gas column
> density as well as density-weighted projections of the sound speed and
> orbital frequency, which I'm using as a proxy for the epicyclic frequency.
>
> Unfortunately, I'm having some trouble making projected maps of the orbital
> frequency.  I've defined two new derived fields, CylinderRadius and
> AngularVelocity (http://paste.yt-project.org/show/1784/).
>
> When I try to project the AngularVelocity field, I get what looks like
> garbage: http://i.imgur.com/PkYhe.png
>
> However, slices work just fine: http://i.imgur.com/NnEbq.png
>
> I've written the derived fields in a coordinate-dependent way, since I'll
> always be doing projections down a fixed axis.  Is that where my problem
> lies?  My understanding of how yt does projections is too shallow to figure
> out exactly what's going wrong here, so I'm hoping the collective wisdom of
> the yt developers and user base can come to the rescue.
>
> Best regards,
> Nathan Goldbaum
> Graduate Student
> Astronomy & Astrophysics, UCSC
> goldbaum at ucolick.org
> http://www.ucolick.org/~goldbaum
>
>
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>
>
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