Learning Forum

[Genf]

Hello,   I'm using fluent meshing mode to create mesh. When I create surface mesh, I get the error message:   error: arg(3rd) out of range in substring   error object: 6   Can anyone help me to find the possible reason?       Thank you,

[Rob]

Pictures and setting will help. Remember to post images in with the text as staff are not permitted to open/download attachments. 

[Genf]

watertight geometry workflow is used 

 

Thank you,

[Rob]

I wonder if it's the Student version hitting the cell cap.  Increase the smaller cell size by a fair bit and see if it'll work. Then try and refine. You're capped at 512k cells, so if you have that many vertices I suspect you're creating too big a mesh. 

[Genf]

hi,

I increased the minimum cell size to 5, it still has this message. I'm using academic license.

I used these settings to generate mesh on my old computer using ANSYS 2019 R2, it worked.

But after I transfer the model to a new computer and use the same settings, the error message came up. The ansys version on the new computer is 2019R3.

thank you

 

[Rob]

Meshing didn't change that much. Were you using Student on the old computer? Given the number of surface facets I don't see how it could work on Student. 

[Genf]

I'm using academic license on both computers. the problem may be caused by different versions of ansys. I have tried other fluent mesh files. Sometimes when I just open the mesh file and click on create surface mesh, the error message shows up:

Error: arg(3rd) out of range in substring

Error Object: 6

Error: Illegal Variant cast from bool to class std::basic_string,class std::allocator >, data: False

Error Object: ()

 

thank you

[Rob]

Teaching or research?  Also, what's the new computer & folder (full path) called?

[Genf]

Research, 

computer name: Untaroiu-2

fluent : C:Program FilesANSYS Incv195fluentntbinwin64

  

 

[Rob]

Not sure then: can you mesh a simple cube? 

[Genf]

yes, it works with a simple cube.

[Rob]

So it's model dependent. Pick a big cell size (ie far larger than will resolve the flow features) and try again. I don't care about mesh quality, I want to see what the cell count is. 

[Genf]

Hi, I tried different settings for a simple cube. It also has errors some time. It seems like when a local size is added, the error message comes up.

[Rob]

What's the local sizing set to? Also how big is the box?

[Genf]

 The box is 21x21x30 mm, Local sizing: 5,

  

[Rob]

Weird. That should give you about 4-6 cells on each edge. I assume the guide "cubes" are a sensible size?

[Genf]

Hi, what are guide cubes ?

[Rob]

The green cube (they're red on my display). They show the expected cell size, you'll typically see two sizes for a min & max. Can you turn off proximity: I wonder if you've created an impossible set of conditions for the mesh. Ie the surface mesh can't be true for both the local & surface sizing. 

[Genf]

The proximity is turned off, but still the same message. The error occurs when reading the temporary .sf file. When I remove the local sizing, it works with the same setting under 'create surface mesh'.

If I make the local sizing on all the surfaces same as the minimum size under 'create surface mesh', What possible changes can local sizing add to the mesh? Is the local sizing information stored in .sf file ? Is it possible to view the details in .sf file ?

 

[Rob]

The sizing on the surface will be a function of the size functions and local sizing. Given it's a cube curvature is unlikely to do much, so sizing will be set by proximity. You can probably get the size function out from the tree (not the workflow) but I'll leave that for you to find: I rarely use that feature. 

[Genf]

thank you for the explanation. The errors occurs when I transfer files to a different computer (same settings), so I doubt it might be caused by software installation.

But do you have suggestions on how to set element size on a specific surface in fluent meshing mode ?

I'm new to fluent meshing, Do you recommend to use workflow in fluent  for mesh generation ?

Thank you

[Rob]

I tend to use the new Watertight Workflow for most problems, but also don't tend to use much local sizing. In your case I think the surface sizing is conflicting with the proximity function, try 4-5 cells across the "gap" and see what happens. 

[johnfound94]

Hi,

I have the same problem. I don't have the academic licence.

Did you solve it?

Please tell me about

Thank you

[Rob]

Which licence are you using?

Can you check the origin position of the model: I've seen one where the origin was miles (literally) away from the origin and tolerances meant the CAD surfaces weren't valid. 

[johnfound94]

 I know that the problem is in "Add a local sizing" following the Watertight, when I create a label it compares that kind of error. Otherwise no.

I'm using the academic licence.

[Genf]

I didn't solve the problem. It occurs on ansys 2019 R3.

I'm using  2019 R2 now.

[Rob]

Checking here in 2019R2 and it works fine, but the default size for local sizing is significantly smaller than the global minimum size. 

[jcastel]

did you ever figure out what was causing this issue?
I keep getting the same error message
"Error: arg(3rd) out of range in substring
Error Object: 6"

[johnsalman]

Hello
I am beginner to ANSYS Fluent but I also faced this problem (Error: arg(3rd) out of range in substring ) , I had solved it by starting a new project totally since it happened to me when I changed the geometry and kept the the setting of the fluent as of previous project. I know this could be classified a dumb solution but it worked with me

[lkang]

.

Hi everyone,

I found the reasons. If the default names are used for local sizing, the error disappears.

Kind regards

.

[Fluidynamic]

.

Thank you Ikang!!! It is! when I keep the default names, the error was disappeared. this problem has confused me many times. Coz before I also meet some situation is when I rename the fluid region, the problem will be disappeared, and there always have some strange problem with Fluent Meshing, they should solve this problem.

.