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Problem with cell area calculation in a slice

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Old   February 27, 2014, 06:46
Default Problem with cell area calculation in a slice
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Hello everybody,

I want to do some tumble evaluation of a cylinder flow. Therefor I need the area of each cell.
So I'm trying to calculate the area of each cell in a slice of my cylinder geometry.

I chose the filter Mesh Quality and set the "triangle-" and "quad quality measure" to "area". The quality column of the resulting spreadsheet shows the area of each cell.
I tested this method with some easy blockmesh geometry (square cross section) and it worked well. (I summed all values up and compared it with the area of the cross section)

However it doesnt work for my clinder. The sum of the cell areas is too low. The problem is that the area of some quad cells is calculated to be 0. This goes for small and bigger cells and seems to be randomly. The area of the marked cell in the screen below is zero. Also most of the other big cells around it. But not all of them are calculated wrong.

What I tried so far:
- Other paraview version. Im using 3.10.1 and I tested it with 4.1.0 too. Result: Same problem...
- I tried it with more triangles than in the screenshot below. Result: Only the area of the triangles was calculated. All the square areas were calculated to zero.

I hope anyone got some idea what could be the problem.

Thank you in advance!
example.jpg
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Old   March 1, 2014, 08:13
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Bruno Santos
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Hi daniel87,

I've seen this issue in the past as well, although it wasn't forum related, so I haven't written anything on this topic yet.

The problem was that the faces in the section cut weren't all pointing to the same direction, or that the order of the points was bad... or that squares simply couldn't be calculated.

Problem is that I can't find a case where I can reproduce this. Can you please share a VTK file of the slice for which you need to calculate the areas?

Best regards,
Bruno
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Old   March 6, 2014, 07:15
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Hi Bruno,

Thank you for your reply!

Im not really familiar with Paraview. Is it possible to export just the slice? Because Im not allowed to upload the whole geometry.
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Old   March 6, 2014, 15:37
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Quote:
Originally Posted by daniel87 View Post
Is it possible to export just the slice?
Quick answer:
  1. Select the slice item in the "Pipeline Browser".
  2. Menu "File -> Save Data".
  3. Save as VTK. Note: You might get more than one file...
  4. Zip the VTK file(s) and attach
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Old   November 21, 2014, 12:56
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Damian B.
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Hello everyone,
I also dealing with this problem. I used the Paraview Quality filter to calculate the area of each cell in a defined slice (Fluent -> Ensight Gold format), it works fine, except the calculation of polygon areas, the result is always -1.

It seems there is a bug in the current Paraview rel. 4.01 or misunderstanding on my side, have anyone an idea ?

Damian
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Old   October 24, 2015, 16:18
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Greetings Damian,

I've had your question on my to-do list and I've finally taken a look into this.
The latest ParaView 4.4.0 documentation states that only the following shapes are supported: http://www.paraview.org/ParaView/Doc...shQuality.html
Quote:
This filter creates a new cell array containing a geometric measure of each cellís fitness. Different quality measures can be chosen for different cell shapes. Supported shapes include triangles, quadrilaterals, tetrahedra, and hexahedra. For other shapes, a value of 0 is assigned.
Sorry for the late reply, but you correct in your suspicion of ParaView's ability.

Best regards,
Bruno
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