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Old   January 3, 2001, 20:25
Default Negative Volume
  #1
sen
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I am getting the message Error # 70 : Cells with negative Volume or volume less than specified value, when I run a check for Illegal and Bad cells, using Star-CD.

What is this and how can I resolve this problem ? How can I find which cells are affected by this ?

I do not see any unconnected cells when I visualize the mesh and I think that my geometry set up and meshing is fine. I am modeling a Wind-Tunnel in 3D.

I have tried several meshes, but still get the same error message again and agin.

Thanks for your help.
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Old   January 8, 2001, 07:32
Default Re: Negative Volume
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Sabatini
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hay tray to make the following kommande. cset all check,cset,,right cset,news,prang,4,-1,0 cflip,cset,,,right sabatini
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Old   January 19, 2001, 00:43
Default Re: Negative Volume
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Fred Ross
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Cflip can be a dangerous command if not used carefully.

If you reflect a model, this inverts all the fluid cells definitions. For this, you need to use the cflip command to fix.

For negative volume cells which are caused by mesh warpage or skew, using the cflip can cause a real mess and be very hard to undo. You start to invert a cell definition next to a perfectly good cell.

Once the cflip is done, if you try to unskew the mesh, you then find out that the volume gets worse since the cell difinitions is now wrong. To find out which ones are now flipped and which ones are correctly defined is near impossible, and you need go back to the model before the cflip command has been issued.

The real fix is to try and add more volume to the cell by unskewing the cell.
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