[yt-users] Star Speeds

[Matthew Turk]

Hi John,
On Apr 7, 2014 10:17 PM, "John Wise" <jwise at physics.gatech.edu> wrote:
>
> Hi Munier,
>
> In v2.x, it seems like the interpolated star velocities aren't defined in
the Enzo-specific fields in frontends/enzo/fields.py, even though that the
metallicity_fraction, creation_time, and dynamical_time fields are defined.
 However, the machinery is there to create these fields.
>
> You can put the following in your .yt/my_plugins.py file or at the
beginning of your script or add it to Enzo's fields.py file.
>
> from yt.data_objects.field_info_container import ValidateSpatial
> from yt.frontends.enzo.fields import _star_field
> add_field('star_particle_velocity_x', function=_star_field,
>           validators=[ValidateSpatial(0)])
> add_field('star_particle_velocity_y', function=_star_field,
>           validators=[ValidateSpatial(0)])
> add_field('star_particle_velocity_z', function=_star_field,
>           validators=[ValidateSpatial(0)])
>
> With v3.0, this code looks like it will still work because _star_field is
still defined.
>
> However one new feature in 3.0 is particle filters, where you can single
out the star particles and then use a deposit operator to interpolate it to
the grid.  Here's what I tried, but I couldn't get it to work.  Maybe
someone more familiar with 3.0 can chime in.  I tried for about 15-30
minutes, but I'm out of time now.  It'd be great to see an example like
this.  I couldn't figure it out from YTEP-0013...
>
> @particle_filter("star", ["particle_type"])
> def finest(pfilter, data):
>     return data["all", "particle_type"] != 1

Ah, here's the trick- filters can't act on unions, and "all" is a union. If
you try it on "io" it should work.

Matt

>
> def _my_star_field(field, data):
>     pfield = "particle_" + field.name[5:]
>     pos = data["star", "Coordinates"]
>     d = data.deposit(pos, [data["star", pfield], data["star",
"particle_mass"]], method = "weighted_mean")
>     return d
>
> add_field(name = ("deposit", "star_velocity_x"), function =
_my_star_field, validators=[ValidateSpatial()])
> add_field(name = ("deposit", "star_velocity_y"), function =
_my_star_field, validators=[ValidateSpatial()])
> add_field(name = ("deposit", "star_velocity_z"), function =
_my_star_field, validators=[ValidateSpatial()])
>
>
> Cheers,
> John
>
>
> On 04/07/2014 07:56 PM, Munier Azzam Salem wrote:
>>
>> Hey Guys,
>>
>>          I'm looking to work with star particle velocities, ideally:
>> some sort of mass-weighted-average of star particle velocities within a
>> given cell (I'm using enzo, if that's relevant). This doesn't seem to
>> exist in th universal field list, although the cic_particle_velocity_x
>> <
http://yt-project.org/docs/dev/reference/field_list.html?highlight=field%20list#cic-particle-velocity-x>/y/z
in
>>
>> the enzo field list seem relevant.
>>
>>          Any advice?
>>
>>                 thanks!
>>                      Munier
>>
>> --
>> Munier A. Salem // 845.489.6450
>>
>>
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>>
>
> --
> John Wise
> Assistant Professor of Physics
> Center for Relativistic Astrophysics, Georgia Tech
> http://cosmo.gatech.edu
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