"divergence detected in amg solver ads-0" after improving meshing using TUI commands

harshabose · January 27, 2019, 10:58

mesh orthogonal quality reduced after creating inflation on wing surface.

I used inflation on wing surface according to the Y+ values needed for my problem. This reduced my orthogonal quality to order of e-03. I tried to improve the mesh by using TUI commands and then the orthogonal quality improved to e-01. Was happy with the result but, when I initialized the problem it showed this error.
divergence detected in amg solver ads-0
Then i tried with my original mesh and everything was cool. Does this orthogonal quality even matter? only thing i know about orthogonal quality is that it should be close to 1. Any comments are appreciated.

RcktMan77 · January 28, 2019, 19:54

Yes, it matters and it's a big deal. You want your mesh's cell face normals to be aligned with the flow direction as much as possible in order to reduce numerical error. In your case, the error is destabilizing your problem likely due to poor mesh quality when you attempt to create a boundary layer resolved mesh.

harshabose · January 29, 2019, 11:14

Thanks for the comment. Can you give me tips for getting a good orthogonal quality mesh with inflation?

RcktMan77 · January 29, 2019, 11:51

It sounds like you're using Fluent, which isn't something I use regularly for mesh generation or as my preferred flow solver. Perhaps others here who use those tools can comment.

January 27, 2019, 10:58	"divergence detected in amg solver ads-0" after improving meshing using TUI commands	#1
harshabose New Member LyLy Join Date: Jan 2019 Posts: 14 Rep Power: 7	mesh orthogonal quality reduced after creating inflation on wing surface. I used inflation on wing surface according to the Y+ values needed for my problem. This reduced my orthogonal quality to order of e-03. I tried to improve the mesh by using TUI commands and then the orthogonal quality improved to e-01. Was happy with the result but, when I initialized the problem it showed this error. divergence detected in amg solver ads-0 Then i tried with my original mesh and everything was cool. Does this orthogonal quality even matter? only thing i know about orthogonal quality is that it should be close to 1. Any comments are appreciated.

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January 28, 2019, 19:54		#2
RcktMan77 Senior Member Zach Davis Join Date: Jan 2010 Location: Los Angeles, CA Posts: 101 Rep Power: 16	Yes, it matters and it's a big deal. You want your mesh's cell face normals to be aligned with the flow direction as much as possible in order to reduce numerical error. In your case, the error is destabilizing your problem likely due to poor mesh quality when you attempt to create a boundary layer resolved mesh.

January 29, 2019, 11:14		#3
harshabose New Member LyLy Join Date: Jan 2019 Posts: 14 Rep Power: 7	Thanks for the comment. Can you give me tips for getting a good orthogonal quality mesh with inflation?

January 29, 2019, 11:51		#4
RcktMan77 Senior Member Zach Davis Join Date: Jan 2010 Location: Los Angeles, CA Posts: 101 Rep Power: 16	It sounds like you're using Fluent, which isn't something I use regularly for mesh generation or as my preferred flow solver. Perhaps others here who use those tools can comment.