Dynamic meshing in CFX: (negative volume error)

vmlxb6 · August 26, 2010, 02:30

Hello,

I am studying the displacement of a cylinder due to the vortex separation caused by the flow of fluid over it. I have meshed a 2-d cylinder in Gambit and running it in CFX.

After 5 iterations I get the following error:

ERROR #002100012 has occurred in subroutine cVolSec. | | Message: |
| A negative ELEMENT volume has been detected. This is a fatal |
| error and execution will be terminated. The location of the first |
| negative volume is reported below. |
| Volume : -0.2583E-07 |
| Location : ( -0.52179E-01, -0.24773E+01, -0.15000E-01)

CFD Solver: The mesh is invalid or folded

Can I repair the mesh in ICEM or something !!!!

ghorrocks · August 26, 2010, 07:48

Your mesh has folded due to excessive mesh deformation. To debug it see this post:

http://www.cfd-online.com/Forums/cfx...modelling.html

The best approach will depend on what the motion is expected to be and What constraints you have on your mesh.

vmlxb6 · August 26, 2010, 13:32

My case is really simple. Its just a cylinder in a rectangular domain. I have attached the jpg image also. When the velocity was 1 m/s it gave 5 iterations while when i reduced it to 0.001 m/s it gave 7 iterations. further reduction gave the same 7 iterations.

Can I alter or repair the mesh in ICEM ???? Is it to do anything with the mesh conditions at the cylinder wall or boundary ?????

a.m. · August 26, 2010, 16:36

To repair mesh you should try to import mesh into ICEM and check it (Edit Mesh -> Check Mesh). But I suggest to check boundary conditions first.

ghorrocks · August 27, 2010, 07:40

As I said, read the other post I linked to. What you need to do is set up a run with mesh motion only and output the results every time step. Then you can see exactly what the problem is.

The problem is not the quality of the mesh, that looks fine.

vmlxb6 · August 27, 2010, 16:38

Hey,

I ran for mesh motion only. Disabled everything in the expert parameter options. It still ran for just 5 iterations giving output files. These files are in .trn format.

When I go to the post processor and load result files it gives the following error:

Error reading number of domains (G/NZN).

What are the other methods to load the result files???

ghorrocks · August 28, 2010, 07:43

Make sure they are full results files. If you only save selected variables you might not be able to read them in.

August 26, 2010, 02:30	Dynamic meshing in CFX: (negative volume error)	#1
vmlxb6 Senior Member Ugly Kid Joe Join Date: Aug 2010 Posts: 193 Rep Power: 16	Hello, I am studying the displacement of a cylinder due to the vortex separation caused by the flow of fluid over it. I have meshed a 2-d cylinder in Gambit and running it in CFX. After 5 iterations I get the following error: ERROR #002100012 has occurred in subroutine cVolSec. \| \| Message: \| \| A negative ELEMENT volume has been detected. This is a fatal \| \| error and execution will be terminated. The location of the first \| \| negative volume is reported below. \| \| Volume : -0.2583E-07 \| \| Location : ( -0.52179E-01, -0.24773E+01, -0.15000E-01) CFD Solver: The mesh is invalid or folded Can I repair the mesh in ICEM or something !!!!

August 27, 2010, 16:38	@ Ghorrocks	#6
vmlxb6 Senior Member Ugly Kid Joe Join Date: Aug 2010 Posts: 193 Rep Power: 16	Hey, I ran for mesh motion only. Disabled everything in the expert parameter options. It still ran for just 5 iterations giving output files. These files are in .trn format. When I go to the post processor and load result files it gives the following error: Error reading number of domains (G/NZN). What are the other methods to load the result files???

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August 26, 2010, 07:48		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,844 Rep Power: 144	Your mesh has folded due to excessive mesh deformation. To debug it see this post: http://www.cfd-online.com/Forums/cfx...modelling.html The best approach will depend on what the motion is expected to be and What constraints you have on your mesh.

August 26, 2010, 16:36		#4
a.m. New Member Alex Join Date: Mar 2010 Location: Russia Posts: 19 Rep Power: 16	To repair mesh you should try to import mesh into ICEM and check it (Edit Mesh -> Check Mesh). But I suggest to check boundary conditions first.

August 27, 2010, 07:40		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,844 Rep Power: 144	As I said, read the other post I linked to. What you need to do is set up a run with mesh motion only and output the results every time step. Then you can see exactly what the problem is. The problem is not the quality of the mesh, that looks fine.

August 28, 2010, 07:43		#7
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,844 Rep Power: 144	Make sure they are full results files. If you only save selected variables you might not be able to read them in.