Mesh error... or not?

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1

I’m now attempting to refine a mesh based on best practices from @retsam which worked very well. Unfortunately I’m consistently getting a mesh error. The SimScale front end gives me the following error:
The mesh did not pass validity checks. Increasing the mesh fineness or adding local refinements to geometrical details potentially fixes this issue. Please contact our support for further assistance.
However when I go into the meshing log, I see a series of iterations removing illegal faces until this is reached:

44%20AM
44%20AM764×776 33.9 KB

@jousefm any ideas?
Project here: https://www.simscale.com/workbench/?pid=6869950879105363263&mi=spec%3Aaad0a8a3-d5ca-461d-b235-d2daa9a0c175%2Cservice%3AMESHING%2Cstrategy%3A39&sh=3

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Hi @jhartung; I see you run now simulation after simulation and dare to cancel them as well. Very good!

In your mesh log you should pay attention on results of Boundary layer report near the meshing log end. You have a lot of tiny faces, quite few are not having the benefit of going to 5 bounding layers extension (you should expect something like 4-5), hence a risk that some regions could impact simulation quality. It looks like that (fragment):

patch                     faces    layers   overall thickness
                                            [m]       [%]
-----                     -----    ------   ---       ---
solid_0_solid_0_face_0    102      2.46     0.0111    59.6    
solid_0_solid_0_face_2    798      4.07     0.0155    83.5    
solid_0_solid_0_face_3    166      5        0.0117    62.9    
solid_0_solid_0_face_4    798      4.08     0.0156    84      
solid_1_solid_1_face_0    4019     4.57     0.0236    91.6    
solid_1_solid_1_face_1    2633     3.64     0.0159    81.2    
solid_1_solid_1_face_2    1605     4.28     0.02      90.6    
solid_1_solid_1_face_3    668      4.21     0.0261    91.1    
solid_1_solid_1_face_4    680      4.26     0.026     91.8    
solid_1_solid_1_face_8    4305     4.66     0.0233    92.6    
solid_1_solid_1_face_11   60       0        0         0       
solid_1_solid_1_face_12   8879     4.45     0.0217    90.8    
solid_1_solid_1_face_13   5611     4.37     0.0221    90.2    
solid_1_solid_1_face_14   125      5        0.0246    92.7    
solid_1_solid_1_face_15   1102     5        0.0218    95.5    
solid_1_solid_1_face_16   479      4.92     0.0193    95.9    
solid_1_solid_1_face_17   100      5        0.0193    95      
solid_1_solid_1_face_18   85       5        0.018     97.2    
solid_1_solid_1_face_19   57       5        0.0184    93.3    
solid_1_solid_1_face_20   85       4.76     0.0177    95.2

As I do not know what validity checks are really doing, this is a hint only about possible culprit. I suppose you can find some additional information on Inflating boundary layers in other forum posts.

Cheers,

Retsam

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3

Thank you @Retsam. When you point these things out, they seem really simple.

Here’s the best forum post I could find for proper y+

In fact, I was probably several orders of magnitude too thick on my boundary layer. I made the simple excel calculator there and ended up with the final layer thickness as a function of expansion ratio and y+=1 for my reference length from the calculator here: http://www.pointwise.com/yplus/

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4

Hi there!

What Andrzej (@Retsam) said is indeed correct and should be taken care of. I also assume that his answer clarifies the doubts you had in this post: Simscale not showing Y+ in Post-Processing - #22 by jhartung, correct? :slight_smile:

Best,

Jousef

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5

Well I no longer had any doubts: I was definitely wrong in that post. 99% sure it was just a scaling problem.

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