[Paraview] Questions regarding: volume calculation, xyplot along a curve and tensor calculation

[Berk Geveci]

Hi Jie,

> 1) Volume calculation:
> I found that the "integrate variables" over a sphere clip never gives
> the correct volume. For example, I tried to use a very simple geometry
> and a very fine mesh (a 200x200x200 micron cube with 2 micron cube
> elements), and use paraview to generate a sphere clip that has radius
> of 50 micron in the center of that cube, then I apply the "integrate
> variables" filter to the clip and show the "Cell Data", it gives a
> volume of 4.78818e-13 instead of 5.236e-13, which is 4/3*pi*r^3. The
> discrepancy is so large that it just cannot be due to the coarseness
> of the mesh. Different mesh and different size of clips gives
> different discrepancies, and I cannot find any obvious relationship
> between the paraview-calculated volume and the real volume.

When I create a 100^3 wavelet and clip it with a sphere of radius 20,
I am getting a volume of 33447.5 which is pretty close to the analytic
value of 33510.3. Can you send me a dataset that demonstrates this
problem?

> 2) X-Y plot: how can I do a xyplot of a scalar along a curved line?
> For example, if I have the pressure field data from a
> flow-around-a-cylinder case, I want to plot the pressure along the
> surface of the cylinder as a function of angle or arc length.

You can't, yet. I am working on that feature for the next release.

> 3) tensor calculation: I have the pressure field and velocity field
> calculated from a CFD tool (Transat in my case), how do I calculate
> stress tensors at each point from P V field in paraview?

Let me ask a question back : do you have any Python knowledge? We are
working on making this really simple but currently the array
calculator is too limited and cannot produce tensors. However, this is
doable using the programmable filter.

-berk