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Add layers on the whole surface

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Old   December 17, 2017, 14:20
Default Add layers on the whole surface
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Emanuele De Stradis
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Hi Foamers!

I'm trying to add layers on the whole surface of an hull, but as you can see from the image, layers collapse at one point and restart again after some space. Why this behaviour? I tried to play with all parameters in the snappyHexMeshDict, but didn't find the solution. Can anyone help me to figure out this problem? I would be really grateful. Thank you so much. I attach also my snappyHexMeshDict.

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File Type: jpg layers.jpg (190.9 KB, 35 views)
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File Type: c snappyHexMeshDict.c (3.3 KB, 7 views)
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Old   December 17, 2017, 18:31
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Taher Chegini
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Try setting the featureAngle to 360. There are some other tweaks that can be done to improve the performance but featureAngle is the main one that control the termination of the layer.
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Old   December 17, 2017, 20:48
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Hi Taataa, thank you so much for your reply I'll try and let you know the results. Thank you again.

Emanuele
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Old   December 18, 2017, 04:16
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Hi! As you told me I tried setting the featureAngle to 360, but it didn't work, the results has not changed what can I do? Thank you again.

Emanuele
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Old   December 18, 2017, 10:09
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Taher Chegini
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You need to give more information then. What is the reasons that you set such set such large values for maxLocalCells and maxGlobalCells? Why you set 180 for resolveFeatureAngle? Why such large values for finalLayerThickness and minThickness? Take a look at the log file and see if there is any error related to the layering part. It's the last job that is done so it should be close to the end.
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Old   December 18, 2017, 10:22
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Emanuele De Stradis
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Thank you for your reply I'm new in openFoam so I can't answer very well to your questions. Anyway, I have 13000000 of global cells in this problem, so to be sure I put those high numbers (I don't know if that can be a problem). For the resolveFeatureAngle I tried different values and it seems that with that value I've obtained the best result for now. For the layer thickness, my supervisor told me to put that values in order to have more large layers. The log file doesn't show any error, also checkmesh is perfect. Can you tell me something about that values and which is the best solution to improve my mesh? I will appreciate it very much. Thank you.
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Old   December 18, 2017, 13:26
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I see. So I would suggest to take at this link to get a sense of the parameters as well as some good starting values. All these setting can affect the layer specially the angles, I would suggest to use 60 for the resolveFeatureAngle and 360 for featureAngle. Then set the maxLocalCells to 3 mil and max global to 15 mil. If you didn't get a good results then try to set the relativeSizes in layer setting to false and give a suitable absolute value for the layers thickness. By absolute value I mean in meter, for example 0.1 for 10 cm and so. It depends on how much do you want thickness to be.
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Old   December 19, 2017, 04:31
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Thank you so much for your suggestions, now I understand better the meaning of those parameters. However, I tried to change the values as you told me, following also the suggestions on the link you posted, but this didn't solve the problem unfortunately (I tried also with relativeSize false, but it was worse). I attach the new snappy and the file log. I don't know what to do now do you have any other suggestion? thank you for your attention.

Emanuele
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File Type: c log.c (126.3 KB, 5 views)
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Old   December 19, 2017, 12:19
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Emanuele De Stradis
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Any idea? I have to do this for my graduation and time is running out I really need your help. Thank you all.

Emanuele De Stradis
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Old   December 19, 2017, 15:37
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Unfortunately, there is no magic setting that can work for all the problem, it's just a matter of playing with the parameters. The angles and thicknesses are the most important ones. You can start by reducing the minThickness to something like 0.1 and finalLayerThickness of 0.4, keeping the angles at 60 and 360.
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Old   December 19, 2017, 15:40
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Thank you so much for your suggestions. I'll try

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