[yt-users] Trouble projecting a derived field

Nathan Goldbaum goldbaum at ucolick.org
Wed Sep 7 00:30:38 PDT 2011


Hi Andrew,

Thanks for the idea.  Unfortunately, that doesn't seem to be the problem.  I just tried taking the absolute value of R cross V before taking the square root and got the exact same results.

-Nathan

On Sep 6, 2011, at 11:43 PM, Andrew Myers wrote:

> 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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