CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Visualization & Post-Processing Software > ParaView

[OpenFOAM] Problem with cell area calculation in a slice

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   February 27, 2014, 06:46
Default Problem with cell area calculation in a slice
  #1
New Member
 
Join Date: Jun 2013
Posts: 4
Rep Power: 13
daniel87 is on a distinguished road
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
daniel87 is offline   Reply With Quote

Old   March 1, 2014, 08:13
Default
  #2
Retired Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,981
Blog Entries: 45
Rep Power: 128
wyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to all
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
__________________
wyldckat is offline   Reply With Quote

Old   March 6, 2014, 07:15
Default
  #3
New Member
 
Join Date: Jun 2013
Posts: 4
Rep Power: 13
daniel87 is on a distinguished road
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.
daniel87 is offline   Reply With Quote

Old   March 6, 2014, 15:37
Default
  #4
Retired Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,981
Blog Entries: 45
Rep Power: 128
wyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to all
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
__________________
wyldckat is offline   Reply With Quote

Old   November 21, 2014, 12:56
Default
  #5
New Member
 
Damian B.
Join Date: Oct 2014
Location: Stuttgart, Germany
Posts: 3
Rep Power: 12
FluidDam is on a distinguished road
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
FluidDam is offline   Reply With Quote

Old   October 24, 2015, 17:18
Default
  #6
Retired Super Moderator
 
Bruno Santos
Join Date: Mar 2009
Location: Lisbon, Portugal
Posts: 10,981
Blog Entries: 45
Rep Power: 128
wyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to allwyldckat is a name known to all
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 cell’s 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
wyldckat is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Gradient calculation at highly non-uniform cell interfaces ashish.svm OpenFOAM Programming & Development 2 July 13, 2018 18:02
Problem simulating a reactor inlet area using rhoReactingFoam hester OpenFOAM Running, Solving & CFD 0 September 3, 2014 11:10
Cell Zones Recognition Problem Maralady FLUENT 0 June 19, 2013 15:00
Interfacial area density calculation kmgraju FLUENT 0 December 15, 2012 07:41
total cell area Ossi Siemens 5 April 8, 2002 03:14


All times are GMT -4. The time now is 17:31.