[efalpha]

Dear all,

I am trying to simulate a multi-physics flow. In particular, I have a high temperature flow through a pipe surrounded by ambient air. Similarly to "snappyHeatExchanger" example, I create different .stl files for each surface.

The problem is that, after the meshing with snappy, splitMesh do not result the proper regions, i.e. 'env', 'solid' and 'pipe_flow' but instead I get up to 2k new regions. Moreover, the reconstructed pipe surface is coarse and with HOLES (pls see figures).

I tried so far to play with the following increasing initial blockMesh resolution, increasing refinement level, using implicitFeatureSnap, subdivide the .stl's for more dense surface, using admesh to correct the stls, etc. The problem persists.

Please help, I have run out of ideas and the deadline is coming fast. Ι include the "snappyHexMeshDict" here, along with some images, while the full case dir (along with VTK files after snappyHex) can be found at: https://mega.nz/folder/xE0XGAYQ#I2I_DTAlujoTq4YW1mDNbA

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  7  
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

#includeEtc "caseDicts/mesh/generation/snappyHexMeshDict.cfg"

castellatedMesh on;
snap            on;
addLayers       off;

geometry
{
    pipe_flow
    {
        type            triSurfaceMesh;
        file            "pipe_flow.stl";
        regions
        {
            inlet           { name inlet; }
            outlet           { name outlet; }
        }
    }
    env
    {
        type            triSurfaceMesh;
        file            "env.stl";
        regions
        {
            inlet           { name inlet; }
            outlet           { name outlet; }
            walls           { name walls; }
        }
    }
    solid
    {
        type            triSurfaceMesh;
        file            "solid.stl";
        regions
        {
            onOutlet        { name onOutlet; }
            OnInlet        { name OnInlet; }
        }
    }
    pipe_to_solid
    {
        type            triSurfaceMesh;
        file            "pipe_to_solid.stl";
    }
    env_to_solid
    {
        type            triSurfaceMesh;
        file            "env_to_solid.stl";
    }
};






castellatedMeshControls
{

// Settings for the castellatedMesh generation.
    // Refinement parameters
    // ~~~~~~~~~~~~~~~~~~~~~
    maxLocalCells 10000000;   //max cells per CPU core
    maxGlobalCells 20000000; //max cells to use before mesh deletion step
    minRefinementCells 10;  //was 0 - zero means no bad cells are allowed during refinement stages 
    maxLoadUnbalance 0.10;
    nCellsBetweenLevels 2; // expansion factor between each high & low refinement zone



    features
    (

        {
        file "pipe_to_solid.eMesh"; // file containing edge mesh
        level 2;               // level of refinement
        }

        {
        file "env_to_solid.eMesh"; // file containing edge mesh
        level 2;               // level of refinement
        }
    );


    // Surface based refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~
    refinementSurfaces
    {
        env
        {
            level           (1 2);
            regions
            {
                inlet           { level (1 2); patchInfo { type patch; } }
                outlet           { level (1 2); patchInfo { type patch; } }
                walls           { level (1 2); patchInfo { type wall; } }
            }
        }
        pipe_flow
        {
            level           (1 2);
            regions
            {
                inlet           { level (1 2); patchInfo { type patch; } }
                outlet           { level (1 2); patchInfo { type patch; } }
            }
        }
        solid
        {
            level           (1 2);
            regions
            {
                onOutlet        {level (1 2); patchInfo { type patch; } }
                onInlet        {level (1 2); patchInfo { type patch; } }
            }
        }
        pipe_to_solid
        {
            level           (1 2);
            faceZone        pipe_to_solid;
            cellZone        pipe_flow;
            cellZoneInside  outside;
        }
        env_to_solid
        {
            level           (1 2);
            faceZone        env_to_solid;
            cellZone        env;
            cellZoneInside  outside;
        }
    }

    refinementRegions
    {
    } 

      locationInMesh (0.00 0.008 0.015); 
  // locationInMesh (-0.0025 0.001 0.002);
   // locationInMesh (-0.025 0.00 0.05); // TUBE
   // locationOutMesh (0.0040 0.008 0.015); 

    //resolveFeatureAngle 45;
    // resolveFeatureAngle 45;

    resolveFeatureAngle 60;
    featureAngle 30;
}

snapControls
{
    // implicitFeatureSnap    true;
    nSmoothPatch 20;
    tolerance 10;
    nSolveIter 300;//25;
    nRelaxIter 10;
    nFeatureSnapIter 25;
    implicitFeatureSnap true;
    explicitFeatureSnap false;
    multiRegionFeatureSnap false;
}

addLayersControls
{
    layers
    {
        walls
        {
            nSurfaceLayers 2;
            mergeFaces true;
        }
        pipe_to_solid
        {
            nSurfaceLayers 2;
            mergeFaces true;
        }
        env_to_solid
        {
            nSurfaceLayers 2;
            mergeFaces true;
        }
    }

    relativeSizes       true;
    expansionRatio      1.2;
    finalLayerThickness 0.1;
    minThickness        1e-4;
}
writePrecision 6;
mergeTolerance 1e-5;

// ************************************************************************* //

Thank you all in advance for your help.

[efalpha]

I found that the problem is in the geometry: the .stl files are not meshed properly.
The question that could be asked now is with regard to the proper way to make .stl meshes. I will put the question in a new thread.