[yt-users] velocity fields in yt

[Elizabeth Tasker]

Maybe a similar scheme to that used for _DivV? So centre the velocity 
field by averaging the two face values in the appropriate direction 
within def _RadialVelocity?

Ideally, I guess bulk_velocity would also be calculated using 
cell-centred quantities, but I think that is set by the user? In which 
case, it's up to them to decide whether to include the off-set (which 
for a large object is probably negligible).


Matthew Turk wrote:
> Yes, it could be off by 0.5*dx.  To calculate it correctly, do you
> need to center the velocity field by re-filling boundary values?
>
> On Wed, Aug 3, 2011 at 5:23 PM, Elizabeth Tasker <taskere at mcmaster.ca> wrote:
>   
>> Although actually, "RadialVelocity" is one place where it would also be an
>> issue. It doesn't look like that is corrected for Zeus, if x-velocity etc
>> are still face-centred. Am I reading that right?
>>
>>
>>
>> Elizabeth Tasker wrote:
>>     
>>> I was wondering if the x-velocity, y-velocity and z-velocity fields
>>> themselves had been averaged to give a cell-centred quantity. There's no
>>> need for them to be so, I just needed to know before I calculated a
>>> cross-product to find the rotational potential of clouds I'd picked out.
>>>
>>> Thank you for the clarification :)
>>>
>>> Elizabeth
>>>
>>>
>>> Matthew Turk wrote:
>>>       
>>>> Only in the DivV and VoritictySquared fields.  Where else should it be
>>>> made?
>>>>
>>>> On Wed, Aug 3, 2011 at 5:04 PM, Elizabeth Tasker <taskere at mcmaster.ca>
>>>> wrote:
>>>>
>>>>         
>>>>> Hi,
>>>>>
>>>>> Quick question about the baryon velocity fields in yt: has any
>>>>> correction
>>>>> been made for the fact Zeus uses face-centred, not cell-centred,
>>>>> velocities?
>>>>>
>>>>> Elizabeth
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>>>>>
>>>>>           
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