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non-positive volume

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Old   April 13, 2007, 14:18
Default non-positive volume
  #1
someshwar rao
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in fluent while reading the mesh i am getting the error "non-positive volumes exist" grid check failed.. why is this error occurring ??
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Old   April 13, 2007, 14:24
Default Re: non-positive volume
  #2
Adriano
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try to check your mesh in gambit first... maybe, some face is not meshed or same volume does not exist.

Ihope it's helpful. Adriano

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Old   April 13, 2007, 14:28
Default Re: non-positive volume
  #3
someshwar rao
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ya.. from a cylinder ..using substract option i have removed an inner cylinder from the initial cylinder..and i have meshed the remaining annular region using interval count..cooper mesh.. and when i read it using fluent.. it said the above error.. can u say where i did the error

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Old   April 13, 2007, 20:36
Default Re: non-positive volume
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Cristina
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I have had the same problem two days before. I`m not an expert, but I read in another message of this forum that this error may be caused by a very little size of the intervals in your mesh. The program can`t deal with the mesh so it handles the mesh generated as it was composed by negative volumes.

In conclusion, use a mesh less fine (biger size of the intervals). I did it and it works.
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Old   April 17, 2007, 03:44
Default Re: non-positive volume
  #5
Rohan
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Hi guys,

Negative is generated when the equi-angle skew of your voule mesh is 1.

As cristina suggested reduce the size of your face meshes as this would reduce the skewness of your face meshes from where the volume mesh is generated.

In general keep the skewness of your surface meshes to less than 0.7.

Hope these are helpful.

Ta

Regards

Rohan
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Old   April 18, 2007, 13:06
Default Re: non-positive volume
  #6
H.A.S
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Hello, to get rid of the negative volumes , i suggest to use ADAPT region or volume , u an put the Min and MAx , then it will for sure be done . in this way , u will use the ADAPT for only the volume that shows the error or need more intervals .
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Old   April 18, 2007, 18:50
Default Re: non-positive volume
  #7
Hoshang Garda
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If you are using Gridgen, negative volumes are read when the co-ordinate system is specified as left handed. Fluent can only handle right handed co-ordinate systems. Re-specify i,j (eta, zeta) for the gird and try re-importing into fluent.
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