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Old   June 21, 2000, 17:08
Default Grid check failed
  #1
Ellen
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Hi, I created my grid file in I-DEAS, and then imported into Fluent for computation. Just after importing the grid, the "Grid check" command didn't find anything wrong, but after I finished the initialization, there was a warning saying non-positive volumes exist, and this time the grid check also failed, stating that many elements are lefthanded and many nodes lie below the axisymmetric axis. (my computation involved a mass-flow-inlet and a pressure-outlet, and I chose mass-inlet as initialized point.)

I can't figure out where I've gone wrong, if anyone could give me some hint or help, I'd be very grateful.
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Old   June 21, 2000, 17:16
Default Re: Grid check failed
  #2
Sandeep
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For the nodes lying below axisymmetric axis..try a grid translate option in fluent. If ur problem is axisymmetric about X..use Y translate =0.00001 (basically a small value). I had the same problem once with this error and it worked.

For lefthanded cells

do this..

> grid
> modify zones
> repair face handedness

Try this might work..!

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Old   June 22, 2000, 09:44
Default Re: Grid check failed
  #3
Jack Keays
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I alos had the problem with non positive volumes. They only seem to materialise after I initialze. I don't experience any face nadedness problems though. Do you know why fluent suddenly found or created volumes with non positive sizes???
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Old   June 22, 2000, 12:27
Default Re: Grid check failed
  #4
Kai Kang
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I've had this problem, too, when I was generating the grid using Gambit for both hex- and tet- elements. I do not know any reason why, but there is also a grid check in Gambit which is very helpful in finding out which volume in your model is wrong---most of the time I try to change the interval assignments and remesh the volume.
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Old   June 22, 2000, 12:27
Default Re: Grid check failed
  #5
Ellen
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Thanks a lot, Sandeep, I solved this problem by translating my grid a little bit along Y direction. and it seems that if there're nodes lying below the axis for the axisymmetric problem, then non-positive volumes will arise by revolving such nodes, and at the same time cell lefthandedness appears also.

thanks again, all.
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Old   June 23, 2000, 14:42
Default Re: Grid check failed
  #6
Sandeep
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..well sometimes little things like this just happen..!I am so glad we have this discussion forum..!
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Old   June 18, 2009, 14:56
Default Negative volumes for axisymmetric cases
  #7
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this is beacuse I think Fluent wants the non-symmetric variable as positive,

i.e. if the case were symmetric about X, then the values of Y must all be positive, for meshing and grid check. So you must translate the grid in Y such that the minimum and maximum valeus of Y are both >0.

Dont know why this is.
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Old   April 26, 2010, 09:12
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  #8
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srinivas
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can we start simulation though gird check fails????
y grid checking fails actually???
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