Mesh quality

darookie · August 19, 2009, 05:34

Which quality option in ICEM refers to the quality specifications in the ANSYS CFX Solver Manager
-> Minimum Orthogonality Angle
-> Maximum Aspect Ratio
-> Maximum Mesh Expansion factor

Furthermore can you give me a guideline for a good Mesh, because the guidance in the help function of ICEM is not sufficient. After i have reached the requirements(Angle >18, Determinant >0.3,Warpage <45) my simulation still does not converge.
Thanks

cbr · August 19, 2009, 07:58

good convergence besides good mesh quality dependeds on correct boundary conditions, timestep.
Have you looked at CFX guidance? Mesh requirements are described there also

ghorrocks · August 19, 2009, 08:12

The quality requirements are just a guess for "normal" simulations. Some simple simulations work fine with much worse quality meshes. More complex simulations (eg multiphase, transonic, chemistry) often need much higher mesh quality. So the mesh quality requirements for a simulation depend on the type of simulation.

darookie · August 19, 2009, 10:18

I simulate a coal combustion with particle tracking and the simulation struggles to converge the heat transfer equation and the particle source change rates. I thought the first error prone step is the mesh quality. So how can I proove if my grid quality is sufficient

besides the other effects (boundary,problem, timestep)
Maybe the attached residuals can help
http://farm3.static.flickr.com/2478/...2d74020f_o.png
http://farm3.static.flickr.com/2593/...be9af1c2_o.png

ghorrocks · August 19, 2009, 19:25

First look here: http://www.cfd-online.com/Wiki/Ansys...gence_criteria

If you suspect mesh quality is the issue then, as the page says, include the convergence residuals in the output file. Look at it in CFD-Post and confirm that the region of high residuals coincides with the region of poor mesh. This will tell you whether mesh quality is in fact the problem.

Glenn

August 19, 2009, 05:34	Mesh quality	#1
darookie New Member Andrej Hoyningen Join Date: Jul 2009 Posts: 22 Rep Power: 16	Which quality option in ICEM refers to the quality specifications in the ANSYS CFX Solver Manager -> Minimum Orthogonality Angle -> Maximum Aspect Ratio -> Maximum Mesh Expansion factor Furthermore can you give me a guideline for a good Mesh, because the guidance in the help function of ICEM is not sufficient. After i have reached the requirements(Angle >18, Determinant >0.3,Warpage <45) my simulation still does not converge. Thanks

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August 19, 2009, 07:58		#2
cbr New Member Join Date: Aug 2009 Posts: 10 Rep Power: 16	good convergence besides good mesh quality dependeds on correct boundary conditions, timestep. Have you looked at CFX guidance? Mesh requirements are described there also

August 19, 2009, 08:12		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	The quality requirements are just a guess for "normal" simulations. Some simple simulations work fine with much worse quality meshes. More complex simulations (eg multiphase, transonic, chemistry) often need much higher mesh quality. So the mesh quality requirements for a simulation depend on the type of simulation.

August 19, 2009, 10:18		#4
darookie New Member Andrej Hoyningen Join Date: Jul 2009 Posts: 22 Rep Power: 16	I simulate a coal combustion with particle tracking and the simulation struggles to converge the heat transfer equation and the particle source change rates. I thought the first error prone step is the mesh quality. So how can I proove if my grid quality is sufficient besides the other effects (boundary,problem, timestep) Maybe the attached residuals can help http://farm3.static.flickr.com/2478/...2d74020f_o.png http://farm3.static.flickr.com/2593/...be9af1c2_o.png

August 19, 2009, 19:25		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	First look here: http://www.cfd-online.com/Wiki/Ansys...gence_criteria If you suspect mesh quality is the issue then, as the page says, include the convergence residuals in the output file. Look at it in CFD-Post and confirm that the region of high residuals coincides with the region of poor mesh. This will tell you whether mesh quality is in fact the problem. Glenn