[yt-users] Cell Volume in regions

[Daniel]

I was comparing density and temperature to the cell_volume.


On 9 July 2014 20:04, Nathan Goldbaum <nathan12343 at gmail.com> wrote:

> Which fields were you comparing with?
>
>
> On Wednesday, July 9, 2014, Daniel <cunnama at gmail.com> wrote:
>
>> Hi Matt,
>>
>> No, just loading a standard GadgetDataset:
>>
>> bbox = [[0.0, 1000000.0],
>>         [0.0, 1000000.0],
>>         [0.0, 1000000.0]]
>>
>> unit_base = {'UnitLength_in_cm'         : 3.08568e+21,
>>              'UnitMass_in_g'            :   1.989e+43,
>>              'UnitVelocity_in_cm_per_s' :      100000}
>>
>> pf = GadgetDataset("snapshot_050", unit_base = unit_base, bounding_box =
>> bbox)
>>
>> Cheers,
>> Daniel
>>
>>
>> On 9 July 2014 17:58, Matthew Turk <matthewturk at gmail.com> wrote:
>>
>>> Hi Daniel,
>>>
>>> On Wed, Jul 9, 2014 at 10:57 AM, Daniel <cunnama at gmail.com> wrote:
>>> > Hi Nathan,
>>> >
>>> > Thanks for getting back to me.
>>> >
>>> > That is odd, because then if my region includes all the particles I
>>> have
>>> > equal elements in cell_volume and all the other gas quantities?
>>> >
>>>
>>> Yup, that is a bit odd.  How are you loading the data?  Are you
>>> specifying either n_ref or over_refine_factor when doing so?
>>>
>>> -Matt
>>>
>>> > Kind Regards,
>>> > Daniel
>>> >
>>> >
>>> > On 9 July 2014 15:06, Nathan Goldbaum <nathan12343 at gmail.com> wrote:
>>> >>
>>> >> Hi Daniel,
>>> >>
>>> >> The cell_volume field is an alias for ('gas, 'cell_volume'), which for
>>> >> Gadget data corresponds to the volume of octree cells. In general
>>> there will
>>> >> be fewer octree cells than particles.  I'm a little surprised the
>>> numbers
>>> >> are so close since the default option is to refine octree cells when
>>> more
>>> >> than 64 particles are in a cell, although the precise structure of the
>>> >> octree will depend on the particle distribution.
>>> >>
>>> >> Nathan
>>> >>
>>> >>
>>> >> On Wednesday, July 9, 2014, Daniel <cunnama at gmail.com> wrote:
>>> >>>
>>> >>> Hi there,
>>> >>>
>>> >>> I am extracting a region from a Gadget dataset using the sphere
>>> function
>>> >>> and then attempting to access the "cell_volume" field.
>>> >>>
>>> >>> For some reason the number of elements in the cell volume field is
>>> not
>>> >>> equal to the number of particles in the region.
>>> >>>
>>> >>> For example I have 4341760 particles but only 4228930 cell volume
>>> >>> elements.
>>> >>>
>>> >>> I have extracted a sphere which encompassed all the particles and the
>>> >>> number of cell volume elements is then equal.
>>> >>>
>>> >>> Any ideas or advice would be greatly appreciated.
>>> >>>
>>> >>> Kind Regards,
>>> >>> Daniel
>>> >>
>>> >>
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>>> >
>>> >
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>>
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