[Paraview] GradientOfUnstructuredDataSet for vorticity & GridConnecivity error with Unstructured Grid

[Andy Bauer]

There is a bug in the computed Q criterion where the vorticity part was
missing a factor of 0.5. I would suggest you compute Q criterion from the
output of the gradient filter. For the gradient of unstructured data set
filter, if the compute vorticity option is selected its result gets put in
the result array name instead of the velocity gradient. There has been much
confusion on this and it will get fixed in ParaView 4.0.

The stream tracer filter doesn't rely on grid connectivity to traverse the
mesh. You may want to look at the seed source that you're using or maybe
some other parameters of the stream tracer filter.

On Tue, Jul 24, 2012 at 6:54 PM, Mei Chen <mei.chen.web at gmail.com> wrote:

> Hi,
>
> I have paraview 3.14 with 64-bit Win7. I have an ensight file with about 5
> million points. I used GradientOfUnstructuredDataSet to calculate the
> gradient, and use the gradient to calculate the Q-value for vortex
> detection (the Q-criterion).
>
> (1) The selected points does not support any evidence of vortex. Does
> anyone know how the GradientOfUnstructuredDataSet filter work?
>
> (2) I also compute the vorticity (this option is under
> GradientOfUnstructuredDataSet filter) but I did not find any resulted
> variable in the list. I was thinking using it to do vortex detection. Can
> anyone tell me where to find this variable?
>
> (3) The result of stream trace filter is noting (cell/point number is 0)
> as I think it is due to the lack of gird connectivity. I tried GridConnecivity
> filter to make the connection but I failed. The vtkErrorMessage: “Missing
> pedigree node array.”, “This filter cannot handle sub-datasets of type:
> vtkUnstructuredGrid. Skipping block.”, and “ExecuteProcess: Unknown input
> ScalarType.” Can anyone tell me what does the pedigree node mean and how
> can I get streamline with the unstructured grid?
>
> Tons of thank!
>
> Best,
> Mei Chen
>
>
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