Mesh orientation and negative volumes

Nick R · January 9, 2011, 08:08

Hi All,

I'm simulating a 3d airfoil in cfx using icem mesher. I have a problem in cfx solver, I either get negative volumes or floating point overflow errors. It's very frustrating as I've changed things around many times to no avail.
Could mesh orientation cause these errors? I mean if you have some right-handed and some left-handed elements would the solution fail?
Also how can I get rid of negative volume elements? Many thanks.
Nick

ghorrocks · January 9, 2011, 19:42

If you do too much smoothing with ICEM you can get negative volume elements. Be very careful with your smoothing.

Nick R · January 10, 2011, 01:49

Thanks for the answer. I suppose I need to change my blocking scheme. Another error I get is with regard to symmetry boundaries. Although my planes are clearly defined. In ANSYS solver the solution is aborted with the following message:

The symmetry boundary condition requires that the boundary patch |
| mesh faces form a plane or axis. However, face set 4 in the |
| symmetry boundary patch| is not in a strict plane, which means that at least one of its |
| faces is not parallel to the others

I don't know what's going on. I've checked my boundary planes many times. Any ideas? Many thanks.

ghorrocks · January 10, 2011, 16:34

The error means you have elements of that face off the plane, so keep checking to find them.

January 9, 2011, 08:08	Mesh orientation and negative volumes	#1
Nick R Senior Member Nick Join Date: Nov 2010 Posts: 103 Rep Power: 4	Hi All, I'm simulating a 3d airfoil in cfx using icem mesher. I have a problem in cfx solver, I either get negative volumes or floating point overflow errors. It's very frustrating as I've changed things around many times to no avail. Could mesh orientation cause these errors? I mean if you have some right-handed and some left-handed elements would the solution fail? Also how can I get rid of negative volume elements? Many thanks. Nick

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January 9, 2011, 19:42		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 7,008 Rep Power: 60	If you do too much smoothing with ICEM you can get negative volume elements. Be very careful with your smoothing.

January 10, 2011, 01:49		#3
Nick R Senior Member Nick Join Date: Nov 2010 Posts: 103 Rep Power: 4	Thanks for the answer. I suppose I need to change my blocking scheme. Another error I get is with regard to symmetry boundaries. Although my planes are clearly defined. In ANSYS solver the solution is aborted with the following message: The symmetry boundary condition requires that the boundary patch \| \| mesh faces form a plane or axis. However, face set 4 in the \| \| symmetry boundary patch\| is not in a strict plane, which means that at least one of its \| \| faces is not parallel to the others I don't know what's going on. I've checked my boundary planes many times. Any ideas? Many thanks.

January 10, 2011, 16:34		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 7,008 Rep Power: 60	The error means you have elements of that face off the plane, so keep checking to find them.