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[snappyHexMesh] Damaged feature edges after boundary layer addition to other surfacfes

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Old   January 8, 2020, 05:16
Default Damaged feature edges after boundary layer addition to other surfacfes
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X Meng
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Dear foamers,

I am struggling with an issue that, by the stage of snapping, all good. However if I add boundary layers to a surface, it is found that some edges which have no relations to those boundary layers are damaged. Really confusing, cos they shouldn't be affected at all, since they are quite far from the surface with boundary layers and not even mentioned at all in the part of 'addLayersControls'.

Have you met this issue before?

Many thanks!
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Old   January 8, 2020, 05:40
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Can you post your sHM dict?
I am guessing you turned off castellated and snapping before adding layers?

Yours, Nazhmiddin
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Old   January 10, 2020, 03:40
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Hi !
Which OpenFOAM version are you using?



Yann
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Old   January 10, 2020, 04:41
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Quote:
Originally Posted by najimaddin96 View Post
Can you post your sHM dict?
I am guessing you turned off castellated and snapping before adding layers?

Yours, Nazhmiddin
Hi Nazhmiddin,

Thank you for your attention. Yes, I did switch off the first two steps when I added boundary layers, otherwise every time I have to wait a very long time to do castellation and snapping again. Theoretically switching-off the first two steps after I have them already shouldn't be a problem at all, am I right??

Cheers
Xiangyin
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Old   January 10, 2020, 04:49
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Quote:
Originally Posted by Yann View Post
Hi !
Which OpenFOAM version are you using?



Yann
Hi Yann,

Thank you for your attention. The version I am using is v1712.

Cheers
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Old   January 10, 2020, 05:12
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Then I'd definitely give a try to the mergePatchFacesAngle parameter. Check the v1712 snappyHexMeshDict annotated file, in the addLayersControls :

Code:
    // Static analysis of starting mesh

        // When not to extrude surface. 0 is flat surface, 90 is when two faces
        // are perpendicular
        featureAngle 130;

        // When to merge patch faces. Default is featureAngle. Useful when
        // featureAngle is large.
        mergePatchFacesAngle 45;

Cheers,
Yann
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Old   January 10, 2020, 07:00
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Many thanks Yann,

The additional bit works for me, the those edges not related to boundary layers are clear again!

However my simpleFoam-based simulation crashed again after solving this meshing issue, due to a huge number of time step continuity errors. I didn't have this issue at all before boundary layer addition. Which is quite strange and frustrating. Never seen this before.

Cheers
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Old   January 13, 2020, 05:36
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Hi Xiangyin,


I don't think the "mergePatchFacesAngle" could be responsible for this behavior, but maybe something else in the mesh setup and/or the boundary conditions.


Maybe you can check your mesh and how the boundary layers has been extruded near your inlets/outlets. CheckMesh is not reporting any errors?


Cheers
Yann
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Old   January 23, 2020, 05:41
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Hi dear all,

Thank you so much for your time and attention on my issues. And really sorry to reply late after days.

I finally solved the issue with the help from my great tech manager. I made a silly mistake in pressure initialization and BC setup.

The pressure used in simpleFoam is kinematic pressure, but not the practical one we want to monitor. This mistake brought most of the problems I saw in this analysis.
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