snappyHexMesh定义了多域网格（MultiRegion）失败。

[李子橙]

最终需要的区域为fluid和solid两个网格域

fluid.stl网格

solid.stl网格

snappyHexMesh文件

FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
castellatedMesh on;
snap            on;
addLayers       off;
geometry
{
    fluid.stl
    {
        type triSurfaceMesh;
		name fluid;
    }

	solid.stl
	{
	    type triSurfaceMesh;
		name solid;
	}
	inlet.stl
	{
	    type triSurfaceMesh;
		name inlet;
	}
	outlet.stl
	{
	    type triSurfaceMesh;
		name outlet;
	}
};
castellatedMeshControls
{
    maxLocalCells 1000000;
    maxGlobalCells 20000000;
    minRefinementCells 0;
    maxLoadUnbalance 0;
    nCellsBetweenLevels 1;
    features
    (
        {
            file "fluid.eMesh";
            level 2;
        }
		{
            file "solid.eMesh";
            level 3;
        }
	    {
            file "inlet.eMesh";
            level 2;
        }
	    {
            file "outlet.eMesh";
            level 2;
        }
    );
    refinementSurfaces
    {
        fluid
        {
            level (1 2);
			faceZone fluid;
            cellZone fluid;
            cellZoneInside inside;
			insidePoint (30 25 0);
        }
		solid
		{
			level (2 3);
		    faceZone solid;
            cellZone solid;
            cellZoneInside inside;
			insidePoint (120 25 0);
		}
		 inlet
		{

			level (1 2);
			patchInfo
				{
					type patch;
				}
		}
		outlet
		{
			level (1 2);
				patchInfo
				{
					type patch;
				}
		}
    }
    resolveFeatureAngle 30;
    refinementRegions
    {
    }
    locationInMesh (0 0 0);
    allowFreeStandingZoneFaces true;
}
snapControls
{
    nSmoothPatch 5;
    tolerance 1.0;
    nSolveIter 300;
    nRelaxIter 10;
    nFeatureSnapIter 5;
    explicitFeatureSnap false;
    multiRegionFeatureSnap false;
    implicitFeatureSnap true;
}
addLayersControls
{
    relativeSizes true;
    layers
    {
        "STL"
        {
            nSurfaceLayers 1;
        }
    }
    expansionRatio 1.0;
    finalLayerThickness 0.3;
    minThickness 0.1;
    nGrow 0;
    featureAngle 30;
    slipFeatureAngle 30;
    nRelaxedIter 3;
    nRelaxIter 3;
    nSmoothSurfaceNormals 1;
    nSmoothNormals 3;
    nSmoothThickness 10;
    maxFaceThicknessRatio 0.5;
    maxThicknessToMedialRatio 0.3;
    minMedialAxisAngle 90;
    nMedialAxisIter 10;
    nBufferCellsNoExtrude 0;
    nLayerIter 50;
    additionalReporting false;
}
meshQualityControls
{
    maxNonOrtho 65;
    maxBoundarySkewness 20;
    maxInternalSkewness 4;
    maxConcave 80;
    minVol 1e-13;
    minTetQuality 1e-30;
    minArea -1;
    minTwist 0.02;
    minDeterminant 0.001;
    minFaceWeight 0.02;
    minVolRatio 0.01;
    minTriangleTwist -1;
    nSmoothScale 4;
    errorReduction 0.75;
    relaxed
    {
        maxNonOrtho 75;
    }
}
debug 0;
mergeTolerance 1e-6;

triSurface目录下的文件

cellZones文件下并未看到单元定义到solid里面

文件百度链接
链接：https://pan.baidu.com/s/1e86s9shDgtXgaSHis_OYSQ
提取码：oyov

[李子橙]

另外，执行完splitMeshRegions -cellZones后，还会生成一个不知怎么切出来的的网格区域（蓝色部分），我很疑惑

[李东岳]

你这个不是正好分为了固体域和流体域了么

[李子橙]

@东岳 找到问题所在了，因为球体无特征边缘，所以将球体的特征边缘删除即可。
这是我修改后的SnappyHexMeshDict文件

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  6                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.com                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      snappyHexMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

// Which of the steps to run
castellatedMesh true;
snap            true;
addLayers       false;

// Optional
singleRegionName false;

// Geometry. Definition of all surfaces. 
geometry
{
	
    solid.stl
    {
        type triSurfaceMesh;
        
        regions
        {
            solid {name solid_to_fluid;}
        }
        
    }
    
    fluid.stl
    {
        type triSurfaceMesh;

        
        regions
        {
            inlet {name inlet;}
            outlet {name outlet;}
            top {name top;}
            bottom {name bottom;}
            front {name front;}
            back {name back;}
        } 
    }
};

// Settings for the castellatedMesh generation.
castellatedMeshControls
{

    // Refinement parameters
    // ~~~~~~~~~~~~~~~~~~~~~
    maxLocalCells 10000000;
    maxGlobalCells 20000000;
    minRefinementCells 0;
    maxLoadUnbalance 0;
    nCellsBetweenLevels 1;

    // Explicit feature edge refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    features
    (
        {
            file "fluid.eMesh";
            level 1;
        }
    );

    // Surface based refinement
    // ~~~~~~~~~~~~~~~~~~~~~~~~ 
	refinementSurfaces
    {
        solid.stl
        {
            // Surface-wise min and max refinement level
            level (0 0);

            regions
            {
                solid {level (3 3);}
            }
            faceZone solid;
            cellZone solid;
            cellZoneInside inside;
        }
       
        fluid.stl
        {
            // Surface-wise min and max refinement level
            level (0 0);

            regions
            {
                inlet {level (0 0);}
                outlet {level (0 0);}
                top {level (0 0);}
                bottom {level (0 0);}
                front {level (0 0);}
                back {level (0 0);}
            }
            faceZone fluid;
            cellZone fluid;
            cellZoneInside inside;
        }
  
    }

    // Feature angle:
    resolveFeatureAngle 20;	
    
    // Region-wise refinement
    // ~~~~~~~~~~~~~~~~~~~~~~

    refinementRegions
    {
        solid.stl
        {
           mode inside;
           levels ((0 3));
        }
        fluid.stl
        {
           mode inside;
           levels ((0 1));
        }    
    }

    // Mesh selection
    // ~~~~~~~~~~~~~~
    locationInMesh (31.76 17.64 31.56);

    // free-standing zone faces. Not used if there are no faceZones.
    allowFreeStandingZoneFaces true;
}

snapControls
{
    nSmoothPatch 3;
    tolerance 3;
    nSolveIter 30;
    nRelaxIter 10;
    nFeatureSnapIter 10;
}

// Settings for the layer addition.
addLayersControls
{
    
    relativeSizes true;

    expansionRatio 1.2;

       
    finalLayerThickness 0.5;  
    minThickness 0.1;

    // Per final patch (so not geometry!) the layer information
    // Note: This behaviour changed after 21x. Any non-mentioned patches
    //       now slide unless:
    //          - nSurfaceLayers is explicitly mentioned to be 0.
    //          - angle to nearest surface < slipFeatureAngle (see below)
    layers
    {
		
    }

    // If points get not extruded do nGrow layers of connected faces that are
    // also not grown. This helps convergence of the layer addition process
    // close to features.
    // Note: changed(corrected) w.r.t 17x! (didn't do anything in 17x)
    nGrow 0;


        featureAngle 130;		//default
        //featureAngle 180;
        //featureAngle 270;

        // Stop layer growth on highly warped cells
        maxFaceThicknessRatio 0.5;


        nSmoothSurfaceNormals 1;

        // Smooth layer thickness over surface patches
        nSmoothThickness 10;

    // Medial axis analysis

        // Angle used to pick up medial axis points
        // Note: changed(corrected) w.r.t 17x! 90 degrees corresponds to 130
        // in 17x.
        minMedialAxisAngle 90;
        minMedianAxisAngle 90;

        // Reduce layer growth where ratio thickness to medial
        // distance is large
        maxThicknessToMedialRatio 0.3;

        // Number of smoothing iterations of interior mesh movement direction
        nSmoothNormals 3;

        // Optional: limit the number of steps walking away from the surface.
        // Default is unlimited.
        //nMedialAxisIter 10;

        // Optional: smooth displacement after medial axis determination.
        // default is 0.
        //nSmoothDisplacement 90;

        // (wip)Optional: do not extrude a point if none of the surrounding points is
        // not extruded. Default is false.
        //detectExtrusionIsland true;

    // Mesh shrinking

        // Optional: at non-patched sides allow mesh to slip if extrusion
        // direction makes angle larger than slipFeatureAngle. Default is
        // 0.5*featureAngle.
        slipFeatureAngle 30;

        // Maximum number of snapping relaxation iterations. Should stop
        // before upon reaching a correct mesh.
        nRelaxIter 5;

        // Create buffer region for new layer terminations
        nBufferCellsNoExtrude 0;

        // Overall max number of layer addition iterations. The mesher will
        // exit if it reaches this number of iterations; possibly with an
        // illegal mesh.
        nLayerIter 50;

        // Max number of iterations after which relaxed meshQuality controls
        // get used. Up to nRelaxedIter it uses the settings in
        // meshQualityControls,
        // after nRelaxedIter it uses the values in
        // meshQualityControls::relaxed.
        nRelaxedIter 20;

        // Additional reporting: if there are just a few faces where there
        // are mesh errors (after adding the layers) print their face centres.
        // This helps in tracking down problematic mesh areas.
        additionalReporting true;
}

// Generic mesh quality settings. At any undoable phase these determine
// where to undo.
meshQualityControls
{
    // Specify mesh quality constraints in separate dictionary so can
    // be reused (e.g. checkMesh -meshQuality)
    #include "meshQualityDict"

    // Optional : some meshing phases allow usage of relaxed rules.
    // See e.g. addLayersControls::nRelaxedIter.
    relaxed
    {
        // Maximum non-orthogonality allowed. Set to 180 to disable.
        maxNonOrtho 75;
    }

    //minFlatness 0.5;

    // Advanced

        // Number of error distribution iterations
        nSmoothScale 4;
        // amount to scale back displacement at error points
        errorReduction 0.75;
}

// Advanced

//debug 0;
//debug 3;

//// Debug flags
/*
debugFlags
(
    mesh            // write intermediate meshes
    intersections   // write current mesh intersections as .obj files
    featureSeeds    // write information about explicit feature edge
                    // refinement
    attraction      // write attraction as .obj files
    layerInfo       // write information about layers
);
*/

//
//// Write flags

writeFlags
(
    scalarLevels    // write volScalarField with cellLevel for postprocessing
    layerSets       // write cellSets, faceSets of faces in layer
    layerFields     // write volScalarField for layer coverage
);

// Merge tolerance. Is fraction of overall bounding box of initial mesh.
// Note: the write tolerance needs to be higher than this.
mergeTolerance 1e-6;

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

[李子橙]

@东岳 此外，谢谢东岳老师的回复。

[李东岳]

感谢分享