[jojosaxo]

Hi all!

Basically, I would like to mesh a 3D elliptic NACA profile and to create a nice boundary layer mesh.
Unfortunately, the BL collapse at some unexpected point, and is not contine (see image attached).

Do anyone has any clue or advices that can help me to sort it out???

Thank you for your help
Jojosaxo

[ssss]

Try to increase the background mesh refinement , and use featureEdges to improve the snapping and layer adding process

[student666]

Hi all,

sorry to use this thread for my problem, but in some way I think it is quite related.

My personal issue is about layer collapsing between patches: I have an inlet and a wall; inlet patch does not have layers.

Enclosed picture explains better what I mean: at inlet side layers are collapsing in a strange way, and in every patch where I don't want have layers too.

Can someone suggest me what parameter should I modify to solve my problem?

here's an extract of the snappyHexMEsh dictionary:

addLayersControls //add the PATCH names from inside the STL file so STLpatchName_insideSTLName 
{
    relativeSizes false; // was true con false hanno la stessa grandezza
    layers
    {

    wallAsp  {nSurfaceLayers 15;}
    
        
    }

    expansionRatio 1.1;
    thickness 0.008;
    //firstLayerThickness 0.015; //was 0.00018
    minThickness 0.001;
    nGrow 0; // was 1 


    // Advanced settings


    featureAngle 310; // When not to extrude surface. 0 is flat, 90 is right angle.
  //  nRelaxIter 2; // Max# of snapping relaxation iter. Should stop before upon reaching a correct mesh.
    nSmoothSurfaceNormals 50; // Number of smoothing iterations of surface normals
    nSmoothNormals 3;//50 Number of smoothing iterations of interior mesh movement direction
    nSmoothThickness 10;//100 Smooth layer thickness over surface patches
    maxFaceThicknessRatio 0.8; // Stop layer growth on highly warped cells
    maxThicknessToMedialRatio 0.9;//0.9 Reduce layer growth where ratio thickness to medial distance is large
    minMedianAxisAngle 135 ; //135; // Angle used to pick up medial axis points
    nBufferCellsNoExtrude 0;// Create buffer region for new layer terminations
    nLayerIter 20;//20 Overall max number of layer addition iterations
    nRelaxIter 20; //Controls number of scaling back iterations during error reduction stage

}



// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{/*
  maxNonOrtho 65; //180
  maxBoundarySkewness 20; //-1 
  maxInternalSkewness 15; //-1
  maxConcave 80; //180
  minVol -1e33;
  minTetQuality -1e30; 
  minTwist -1e30;
  minDeterminant -1; 
  minFaceWeight -1;
  minVolRatio -1;
  minArea -1;
  minTriangleTwist -1;*/

    maxNonOrtho 65; 
    maxBoundarySkewness 20;   
    maxInternalSkewness 4;   
    maxConcave 80; //80;
    minFlatness 0.5;
    minVol 1e-13;
    minTetQuality   -1e30;//1e-9; // 
    minArea -1;
    minTwist  0.02; //-1e30;
    minDeterminant 0.001;
    minFaceWeight 0.02;
    minVolRatio 0.01;
    minTriangleTwist -1;

    // Advanced

    nSmoothScale 4;
    errorReduction 0.75;
}