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[ANSYS Meshing] Cut Cell /// Meshing Warning and Error

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Old   August 5, 2016, 08:56
Default Cut Cell /// Meshing Warning and Error
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Onur Özcan
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Hi all,

I am using ANSYS-Meshing,

I have seen that there are some warnings and error

Error : one or more elements have an orthogonal quality less than 0.0.Please check your mesh carefully!

Warning : One or more named selection have no mesh associated with them. Either the assembly meshing failed due to tessellation problmes or the size a Named selection is smaller that the min size.

Warning : The tolerance of geometry is larger than the applied tessalliation refinement tolerance. This might lead to an uneven mesh and/or to poor geometric accuracy of the mesh.

Error: Assembly meshing inflation meshing failed.

Anyone hel me will be appreciated!

Kin Regards,
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Old   August 8, 2016, 08:03
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Paritosh Vasava
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All the errors and warnings are self-explanatory.

Post pictures of your model and details of your mesh setup, it will help everyone help you.
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Old   August 9, 2016, 01:43
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Quote:
Originally Posted by vasava View Post
All the errors and warnings are self-explanatory.

Post pictures of your model and details of your mesh setup, it will help everyone help you.
Well,

I have uploded enough pictures. First one contains the geometry that I have created. The geometry consisting of 2 fluid zone and 1 fluid zone. Interfaces are made fluid-fluid (gob and air) and fluid-solid (air-solid)

Second one shows the detail of DM.

Third one shows the gob mesh

Third one shows the total mesh

Last one shows the detail of ANSYS-Meshing.

I have already told you about warning and error.
Attached Images
File Type: jpg geometry.JPG (56.7 KB, 122 views)
File Type: jpg DM.JPG (62.5 KB, 83 views)
File Type: jpg gob-inflation.JPG (120.7 KB, 114 views)
File Type: jpg Mesh.JPG (123.1 KB, 145 views)
File Type: jpg outline.JPG (80.0 KB, 80 views)
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Old   August 9, 2016, 02:26
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  1. Firstly check the location of the bad meshes. The error shows that you have negative volume cells in your mesh.
  2. Is there a particular reason why you are using cutcell method? I would recommend you to switch to other methods to get better local control over the mesh.
  3. The warnings indicate that you may have some faces in your geometry that are so small that they are not meshed with current settings.
    You can either eliminate those by manipulating geometry or use virtual topology settings.
  4. You have created the interfaces but then You have also named the interfaces via 'Named Selection'. This is incorrect. Defining interfaces via 'contact region' setting is enough.
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Old   August 9, 2016, 02:44
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Hi vasava,

Thank you for your help,

Item 4 is clear and cool.
Item 2, I already have tried some other methods ( melt glass,sweep and inflation and all the other zones are tetra (because I have used global mesh sizing,like relevance).But this time skewness is more than 0.98. Because it arise from boundary layer mesh in air zone.

Item 1, I am going to check it

Item 3, Min size has been decreased (by decreasing relevance) and small faces problem will be resolved ! (got it?) But I dont understand what geometry manipulation is and I dont still use Virtual topology as though I have watch some videos.

Kind Regards,
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Old   August 9, 2016, 03:40
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Quote:
Originally Posted by oozcan View Post
But I dont understand what geometry manipulation is and I dont still use Virtual topology as though I have watch some videos.
For example, you can use merge neighboring faces to eliminate smaller faces in domain.

It would still be interesting to see the location of the negative volume mesh elements.
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Old   August 9, 2016, 03:50
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I have merged all regarding faces (and all edges have been merged) in DM. Same DM's are to be used in cut-cell meshing and tetra mesh in different workbench. One has more than 0.98 skewness, other (cut-cell) has same problems.

Really dont know, but I am appreciated what you have done !
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Old   August 9, 2016, 08:58
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Quote:
Originally Posted by oozcan View Post
I....more than 0.98 skewness.........
Did you see this value in Workbench or in Fluent? Ansys meshing may report boundary layer elements as bad quality elements (as they have very small thickness and relatively larger area). However if you import this mesh to fluent, it will be happy to make carry out calculations for the same mesh.

If the mesh passe all the mesh check, then it is alright to use the mesh. Also, fluent has some limited (but good) capabilities of fixing bad meshes. Have a look at commands like 'improve-quality' and 'repair' in fluent.
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Old   August 9, 2016, 09:14
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... divergence detected is always shown in FLUENT calculation when skewness is more than 0.98. As I know that terrible thing, I have never imported Meshing to FLUENT.

I do not prefer using TUI commands. Because I am trying to develop mesh system. if I use TUI commands to improve ''mesh'', another model I will create has same future.

I am really appreciated to you who help me.

Thanks,

Maybe you can help me regarding other posts for same model.
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Old   August 10, 2016, 01:30
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[*]You have created the interfaces but then You have also named the interfaces via 'Named Selection'. This is incorrect. Defining interfaces via 'contact region' setting is enough.[/LIST][/QUOTE]

Hi,

I have tried without naming interfaces .Then FLUENT doesnt provide ''interface'' (only interior).Whereas I need to conjugate heat transfer between solid and fluid zone.I need to define interface named selection
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