[Paraview] Vorticity is calculated as zero

[Andy Bauer]

Hi Andreas,

The best way I can think of to get this working in ParaView is to use the
programmable filter to convert to linear triangles. You can also subdivide
the triangles if you want to maintain your higher order accuracy.

Regards,
Andy


On Wed, May 21, 2014 at 5:32 PM, Andreas Hessenthaler
<hessenthaler at mail.de>wrote:

> Indeed, my smaller mesh had linear triangles. And changing that to
> quadratic triangles gives the same behavior (attachment).
>
> What is the best way to circumvent this?
>
> The reason why I wanna use the vorticity function is the following: eddies
> appear all over the domain and using lines with the streamtracer filter
> gives regions with either no streamlines or regions that are very much
> crowded by streamlines. Therefore, having a vorticity field would be a
> suitable approach to have a nice and clean visualization of the flow field.
>
> Cheers
>
>
> Am 21-May-2014 17:00:55 +0200 schrieb andy.bauer at kitware.com:
>
> It looks like these are quadratic triangles. I'm not sure that the compute
> derivatives filter works with that type of cell. Did your smaller grid also
> have quadratic cell types?
>
>
> On Wed, May 21, 2014 at 9:51 AM, Andreas Hessenthaler wrote:
>
>> Hi Andy,
>>
>> thanks for your quick reply. Please find the *.vtu file attached.
>>
>> Cheers
>> Andreas
>>
>>
>>
>>
>> Am 21-May-2014 15:24:30 +0200 schrieb andy.bauer at kitware.com:
>>
>> Can you share your data set? It will be difficult to diagnose without
>> that.
>>
>>
>> On Wed, May 21, 2014 at 9:06 AM, Andreas Hessenthaler wrote:
>>
>>> Hi there,
>>>
>>> I have the following problem:
>>>
>>> When I calculate the vorticity through Filters > Compute Derivatives >
>>> Vorticity for a simple example (driven cavity in 2D) with only few elements
>>> on an unstructured grid I get the correct values.
>>>
>>> Though, when I do the same for a bigger domain, i.e. more elements (~80
>>> 000 nodes), I only get zero vorticity values.
>>>
>>> The grids and values are all read in from *.vtu files, with the exact
>>> same format, meshes are triangluar 2D (z-components set to 0.0).
>>>
>>> I can reproduce the behavior on different versions of ParaView: 3.14.1 &
>>> 4.1.0 as well as different operating systems: Windows 7 & Ubuntu 14.04.
>>>
>>> If I calculate the gradient of the velocity field, all values are
>>> calculated as zero as well.
>>>
>>> Thanks in advance!
>>>
>>> Cheers
>>> Andreas
>>>
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