Negative Elements in mesh generated by Gridgen

gracerlima · March 16, 2010, 19:44

Hi Everybody!

I generated a mesh in Gridgen in a 2d NACA0012 profile + nearfield geometry and when I checked the mesh in Fluent all the elements turned out to be negative.

I would like to know if anyone has ever faced this problem and if maybe could help me.

The nearfield circle is divided in two semi-circles and also the profile has been divided in the most curved regions.

Thanks in advance for the help!

Regards

rmatus · March 16, 2010, 21:01

Grace:

The most likely cause of this is having a left-handed block definition in Gridgen. You can go into the Block Commands menu and choose Respecify I,J,K to check and correct this.

Another possible cause for negative volumes is to have the grid defined in some plane other than the XY plane.

Hope this helps.

gracerlima · March 16, 2010, 21:25

Matus, thanks a lot!

You gave me a very good idea.

I went to the Bolck Commands menu, and set to modify the block and then Reorient Faces...It worked very well...I've already checked the mesh in Fluent and it is ok!

I am not that familiar with Gridgen so I don't know very well all the commands possibilities!

Thanks a lot for the help!

Best regards!!!

rmatus · March 16, 2010, 21:38

Happy to hear it worked.

March 16, 2010, 19:44	Negative Elements in mesh generated by Gridgen	#1
gracerlima New Member Grace Lima Join Date: Mar 2010 Posts: 7 Rep Power: 5	Hi Everybody! I generated a mesh in Gridgen in a 2d NACA0012 profile + nearfield geometry and when I checked the mesh in Fluent all the elements turned out to be negative. I would like to know if anyone has ever faced this problem and if maybe could help me. The nearfield circle is divided in two semi-circles and also the profile has been divided in the most curved regions. Thanks in advance for the help! Regards

March 16, 2010, 21:01	Left handed block?	#2
rmatus Member Rick Matus Join Date: Mar 2009 Location: Fort Worth, Texas, USA Posts: 57 Rep Power: 6	Grace: The most likely cause of this is having a left-handed block definition in Gridgen. You can go into the Block Commands menu and choose Respecify I,J,K to check and correct this. Another possible cause for negative volumes is to have the grid defined in some plane other than the XY plane. Hope this helps.

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March 16, 2010, 21:25		#3
gracerlima New Member Grace Lima Join Date: Mar 2010 Posts: 7 Rep Power: 5	Matus, thanks a lot! You gave me a very good idea. I went to the Bolck Commands menu, and set to modify the block and then Reorient Faces...It worked very well...I've already checked the mesh in Fluent and it is ok! I am not that familiar with Gridgen so I don't know very well all the commands possibilities! Thanks a lot for the help! Best regards!!!

March 16, 2010, 21:38		#4
rmatus Member Rick Matus Join Date: Mar 2009 Location: Fort Worth, Texas, USA Posts: 57 Rep Power: 6	Happy to hear it worked.