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Need help setting up chtMultiRegion

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Old   September 23, 2019, 09:42
Default Need help setting up chtMultiRegion
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Oskar T
Join Date: Sep 2019
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I am currently learning how to setup a chtMultiRegion problem but I'm having hard time finding a good tutorial or walkthrough on how to set it up.

I have created an incredible easy heat sink which I wish to flow air through. The air will pickup some heat which will be dissipated from the flange which will have an energy flux assigned into it (I believe this is a boundary condition).
I have: A heat sink (solid) inside a "wind-tunnel" (Inlet, Outlet and walls) blowing air.

The sink has been exported from my CAD-software as an '.stl'-file. I have found tutorials showing how to create the mesh and split the regions (using snappyHexMesh) and managed to do just that.

My commands are as follow:
  • blockMesh
  • snappyHexMesh -overwrite
  • splitMeshRegions -cellZones -overwrite

In my boundary condition (0), system and constant folder I now have three folders; domain1, Heater and Outside.
Now I don't know how to continue setting up the boundary conditions and the rest of the case necessary to run a simulation. Any ideas or guidance is appreciated!

snappyHexMeshDict
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
#includeEtc "caseDicts/mesh/generation/snappyHexMeshDict.cfg"
// Which of the steps to run
castellatedMesh true;
snap            false;
addLayers       false;



geometry
{
	Outside
	{
		type	searchableBox;
		min		(-0.1 -0.05 0.001);
		max 	(0.2  0.07 0.1);
	
	}
    Heater
    {
        type triSurfaceMesh;
        file "Faces.stl";
    }
};


castellatedMeshControls
{
	// Specifies a level for any cell intersected by its edges.
    // This is a featureEdgeMesh, read from constant/triSurface for now.
    features
    (
		{ file "Faces.eMesh"; level 3; }
    );



    refinementSurfaces
    {
		Outside
		{
			level	(1 1);
			faceZone	Outside;
			cellZone	Outside;
			cellZoneInside	inside;
		}
        Heater
        {
            level	(2 2);
			faceZone	Heater;
			cellZone	Heater;
			cellZoneInside	inside;
        }

    }
	resolveFeatureAngle 30;
	    refinementRegions
    {
    }
    locationInMesh (0.05 0.01 0.01); // Offset from (0 0 0) to avoid coinciding with face or edge
	allowFreeStandingZoneFaces true;
	maxLocalCells 1500000;
    maxGlobalCells 2000000;
	minRefinementCells 1;
    nCellsBetweenLevels 3;

}



// Settings for the snapping.
snapControls
{
	implicitFeatureSnap true;
	explicitFeatureSnap false;
    nSmoothPatch 3;
    tolerance 2;
    nSolveIter 110;
    nRelaxIter 5;
}




// Settings for the layer addition.
addLayersControls
{
    layers
    {
        "Car.*"
        {
            nSurfaceLayers 15;
        }  
    }

    relativeSizes       false; // false means you specify the minthickness
    expansionRatio      1.15;
//    finalLayerThickness 1e-2;		// Either final or first + expansionRatio must be specified
    minThickness        1e-3;
    firstLayerThickness 2e-3;

//  maxThicknessToMedialRatio 0.6;
	featureAngle 120;

}




// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    minTetQuality -1e+30;
}

/*writeFlags
(
//    scalarLevels
    layerSets
    layerFields
); */

mergeTolerance 1e-6;

// ************************************************************************* //
blockMeshDict
Code:
/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  v1906                                 |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

scale   1;

vertices
(
    (-0.1 -0.05 -0.001) // 0
    ( 0.2 -0.05 -0.001) // 1
    ( 0.2  0.07 -0.001) // 2
    (-0.1  0.07 -0.001) // 3
    (-0.1 -0.05 0.1) // 4
    ( 0.2 -0.05 0.1) // 5
    ( 0.2  0.07 0.1) // 6
    (-0.1  0.07 0.1) // 7
);

blocks
(
    hex (0 1 2 3 4 5 6 7) (30 13 10) simpleGrading (1 1 1)
);

edges
(
);

boundary
(
    Sym1
    {
        type symmetryPlane;
        faces
        (
            (0 1 5 4)
        );
    }
    Sym2
    {
        type symmetryPlane;
        faces
        (
            (3 7 6 2)
        );
    }
    Inlet
    {
        type patch;
        faces
        (
            (0 4 7 3)
        );
    }
    Outlet
    {
        type patch;
        faces
        (
            (1 2 6 5)
        );
    }
    Ground
    {
        type wall;
        faces
        (
            (0 3 2 1)
        );
    }
    Top
    {
        type symmetryPlane;
        faces
        (
            (7 6 5 4)
        );
    }
);


// ************************************************************************* //
STL-file of the heat sink
Code:
solid Volume
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    endloop
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    endloop
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Last edited by OskarT; September 23, 2019 at 11:39.
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Old   September 25, 2019, 16:51
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There are many cht tutorials distributed with OpenFOAM : https://github.com/OpenFOAM/OpenFOAM...ultiRegionFoam. I've not looked at them, but snappyMultiRegionHeater sounds like it'd be helpful.

Caelan
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cht, heat transfer, multi region, snappyhexmesh

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