[Ahyar]

I want to generate mesh from this geometry that i create using freecad and its format is .obj



but when i tried to generate using snappyhexmesh utility, the mesh doesn't come out as i expected, the background mesh outside the geometry still exists and are not removed by snappyhexmesh.



this is my snappyHexMeshDict

/*--------------------------------*- 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;
}

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

castellatedMesh true;
snap            true;
addLayers       false;

geometry
{
    inlet.obj
    {
        type triSurfaceMesh;
        name inlet;
    }
    outletBawah.obj
    {
        type triSurfaceMesh;
        name outlet;
    }
    outletAtas.obj
    {
        type triSurfaceMesh;
        name outlet;
    }
    walls.obj
    {
        type triSurfaceMesh;
        name walls;
    }
}


castellatedMeshControls
{

    maxLocalCells 1000000;

    maxGlobalCells 2000000;

    minRefinementCells 0;

    nCellsBetweenLevels 2;

    maxLoadUnbalance 0.10;

    features
    (
        {
            file "inlet.eMesh";
            level 3;
        }

        {
            file "walls.eMesh";
            level 1;
        }
        {
            file "outletBawah.eMesh";
            level 0;
        }
        {
            file "outletAtas.eMesh";
            level 0;
        }
        
    );

    resolveFeatureAngle 30;

    refinementSurfaces
    {
        inlet
        {
            level (2 2);
        }
        walls
        {
            level (1 1);
        }
        outletBawah
        {
            level (0 0);
        }
        outletAtas
        {
            level (0 0);
        }
    }

    refinementRegions
    {
    }

    locationInMesh (0.0 0.0 0.0); // Inside point

    allowFreeStandingZoneFaces true;
}

// Settings for the snapping.
snapControls
{

    nSmoothPatch 3;

    tolerance 1.0;

    nSolveIter 300;

    nRelaxIter 10;

    nFeatureSnapIter 10;

    implicitFeatureSnap true;

    explicitFeatureSnap false;

    multiRegionFeatureSnap true;
}

// Settings for the layer addition.
addLayersControls
{

    relativeSizes true;

    layers
    {
    }

    expansionRatio 1.0;

    finalLayerThickness 0.3;

    minThickness 0.25;

    nGrow 0;

    featureAngle 30;

    nRelaxIter 5;

    nSmoothSurfaceNormals 1;

    nSmoothNormals 3;

    nSmoothThickness 10;

    maxFaceThicknessRatio 0.5;

    maxThicknessToMedialRatio 0.3;

    minMedianAxisAngle 90;

    nBufferCellsNoExtrude 0;

    nLayerIter 50;

    nRelaxedIter 20;
}

meshQualityControls
{
    #include "meshQualityDict"

    relaxed
    {
        maxNonOrtho 150;
    }
}

writeFlags
(
);

mergeTolerance 1E-6;


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

, what should i change?
and below is my case
tankiFlotation.zip