Mesh morphed error in CCM+

MachZero · April 21, 2017, 07:46

Hey guys. I am trying to do an ice accretion analysis in star ccm+. To do this you have to use mesh morphing. I have an issue that when I do this on a simple wing it works fine. However any other portion of an aircraft, I find that the wall distorts and compresses the first prism layer only. The rest of the volume mesh won't move. Then I get a negative cell. Anyone else see this or know how to get around it?

me3840 · April 21, 2017, 20:50

How thick is the first layer height? If it's very small you might find you need to reduce the morpher tolerance.

MachZero · April 23, 2017, 16:50

The first prism layer is pretty thin. I've done my best to make it so that the aspect ratio isn't too high by refining but that doesn't seem to change anything.

I'll try and drop the tolerance to 1e-10 from 1e-7. I'll report back tomorrow.

Oddly enough I have had this work numerous times on. 2d wing numerous times with pretty large deformations. However with this more 3D shape the morphing seems to struggle.

Thanks for the idea. Any and all ideas welcome.

MachZero · April 24, 2017, 07:27

Well I gave this a shot but it did not work. Same issue occurred. The first prism layer collapses while some but not much movement from the volume mesh is observed.

Any other thoughts?

me3840 · April 24, 2017, 12:28

Maybe try giving a high-reynolds mesh a shot?

MachZero · April 24, 2017, 15:33

I like the idea! First question about that, what is a higher Reynolds mesh?

me3840 · April 24, 2017, 18:52

Well if you have very small first cell heights I'm assuming you're using a low-reynolds wall treatment (no wall function). So if you switch to using wall function this relaxes your first cell height requirement.

MachZero · April 25, 2017, 07:22

Ahh okay I understand what you're saying. Thanks for clarifying. In past studies with more 2d shapes I've found that ice accumulation is very sensitive to y+. Therefore I wouldn't be able to get away with thicker prisms.

I just tried using a poly mesh as well as a trim. Don't not change. Still failed.

Starting to think ccm morphed just isn't robust enough. Have any other thoughts?

Thanks for ideas thus far.

April 21, 2017, 07:46	Mesh morphed error in CCM+	#1
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 15	Hey guys. I am trying to do an ice accretion analysis in star ccm+. To do this you have to use mesh morphing. I have an issue that when I do this on a simple wing it works fine. However any other portion of an aircraft, I find that the wall distorts and compresses the first prism layer only. The rest of the volume mesh won't move. Then I get a negative cell. Anyone else see this or know how to get around it?

April 23, 2017, 16:50	Tolerance	#3
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 15	The first prism layer is pretty thin. I've done my best to make it so that the aspect ratio isn't too high by refining but that doesn't seem to change anything. I'll try and drop the tolerance to 1e-10 from 1e-7. I'll report back tomorrow. Oddly enough I have had this work numerous times on. 2d wing numerous times with pretty large deformations. However with this more 3D shape the morphing seems to struggle. Thanks for the idea. Any and all ideas welcome.

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April 21, 2017, 20:50		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	How thick is the first layer height? If it's very small you might find you need to reduce the morpher tolerance.

April 24, 2017, 07:27		#4
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 15	Well I gave this a shot but it did not work. Same issue occurred. The first prism layer collapses while some but not much movement from the volume mesh is observed. Any other thoughts?

April 24, 2017, 12:28		#5
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Maybe try giving a high-reynolds mesh a shot?

April 24, 2017, 15:33		#6
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 15	I like the idea! First question about that, what is a higher Reynolds mesh?

April 24, 2017, 18:52		#7
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 25	Well if you have very small first cell heights I'm assuming you're using a low-reynolds wall treatment (no wall function). So if you switch to using wall function this relaxes your first cell height requirement.

April 25, 2017, 07:22		#8
MachZero Member Join Date: Aug 2011 Posts: 89 Rep Power: 15	Ahh okay I understand what you're saying. Thanks for clarifying. In past studies with more 2d shapes I've found that ice accumulation is very sensitive to y+. Therefore I wouldn't be able to get away with thicker prisms. I just tried using a poly mesh as well as a trim. Don't not change. Still failed. Starting to think ccm morphed just isn't robust enough. Have any other thoughts? Thanks for ideas thus far.