CFD Online Logo CFD Online URL
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Meshing & Mesh Conversion

[snappyHexMesh] Problem with addLayerControls and non-relative sizes

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By jakethejake

LinkBack Thread Tools Search this Thread Display Modes
Old   August 28, 2019, 08:58
Default Problem with addLayerControls and non-relative sizes
New Member
Join Date: Jul 2015
Posts: 10
Rep Power: 9
jakethejake is on a distinguished road
Dear Foamers,

I'm facing a (at least for me) strange behaviour of the layering part of snappyHexMesh (OF used is the Foundation version v6).

Case setup:
- I have a wall with a refinement region downstream. Therefore I set the relativesSizes to false to have a uniform boundary layer in every region (transition non-refinement to the refinement area). In the base case I used five layers with firstLayerThickness and expansionRatio specified.
- Now I have a case with an increased boundary layer thickness and want to resolve that by modifying the mesh in the region next to the wall. Options: I could either increase the number of layers or increase the first cell height respectively expansion ratio.
- With both options I see there is some kind of a "critical height" of the layer pack where the meshing breaks down the uniform boundary layer and kind of ignores the flag "relativesSizes = false"
--> Result for each option case is that I get a non uniform layer pack between the refinement and non-refinement regions.

Does anyone know how to deal with kind of "critical height" or getting rid of that behaviour? Or is it related to some strange parameters in the advanced settings section?

Find attached the pictures of the castellated mesh and the operations.
1. Castellated Mesh
2. Added five layers (expansionRatio 1.2; firstLayerThickness 0.00015)
3. Added six layers (expansionRatio 1.2; firstLayerThickness 0.00015)
4. Added five layers (expansionRatio 1.25; firstLayerThickness 0.00015)
5. Added five layers (expansionRatio 1.2; firstLayerThickness 0.00017)

Can anyone help?


    // Global parameters
    relativeSizes             false; // false, usually with firstLayerThickness
    expansionRatio          1.2;
    //thickness               0.0015;
    //finalLayerThickness  0.00044;
    minThickness             0.00015;
    firstLayerThickness     0.00015;

    // Per final patch (so not geometry!) the layer information
            nSurfaceLayers 5;
            // Local parameters
            //expansionRatio             1.2;

    // Advanced settings
    featureAngle                 30;    
    slipFeatureAngle             30;

    nGrow                         0;

    nLayerIter                     50;
    nRelaxedIter                 20;
    nRelaxIter                     5;

    nSmoothSurfaceNormals         1;
    nSmoothNormals                 3;
    nSmoothThickness             10;
    maxFaceThicknessRatio         0.5;
    maxThicknessToMedialRatio     0.3;

    minMedialAxisAngle             90;
    minMedianAxisAngle             90;
    nMedialAxisIter               10;

    nBufferCellsNoExtrude         0;
    additionalReporting         false;
Attached Images
File Type: png castellated.png (139.6 KB, 41 views)
File Type: png exp1p2_nl5_fh1p5_baseCase.png (163.2 KB, 41 views)
File Type: png exp1p2_nl6_fh1p5_option1.png (173.4 KB, 36 views)
File Type: png exp1p25_nl5_fh1p5_option2.png (169.7 KB, 28 views)
File Type: png exp1p2_nl5_fh1p7_option3.png (170.6 KB, 29 views)
alexvaleije likes this.
jakethejake is offline   Reply With Quote

Old   January 29, 2023, 06:57
New Member
Join Date: Oct 2022
Posts: 1
Rep Power: 0
Fedegenti is on a distinguished road
Try toggling off decompose polyhedra and triangulate the slice
Fedegenti is offline   Reply With Quote


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 06:05.