openfoam动网格加密后 计算很慢

[Emrys]

各位老师好，我在计算三维多相流流动时采用界面局部加密的动网格，发现时间步长特别小，界面局部加密后的网格67w时间步长1e-7 1e-8左右；
而在全场加密1000w网格情况下计算是正常的时间步长1e-5；
请问是局部加密非结构化网格的原因导致步长很小？ 四面是周期性边界条件，因此采用了cyclicAMI的边界。

/*--------------------------------*- C++ -*----------------------------------*\
  =========                 |
  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
   \\    /   O peration     | Website:  https://openfoam.org
    \\  /    A nd           | Version:  8
     \\/     M anipulation  |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    location    "constant";
    object      dynamicMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

dynamicFvMesh   dynamicRefineFvMesh;

// How often to refine
refineInterval  1;

// Field to be refinement on
field           alpha.water;

// Refine field in between lower..upper
lowerRefineLevel 0.001;
upperRefineLevel 0.999;

// If value < unrefineLevel unrefine
unrefineLevel   10;

// Have slower than 2:1 refinement
nBufferLayers   1;

// Refine cells only up to maxRefinement levels
maxRefinement   2;

// Stop refinement if maxCells reached
maxCells        20000000;

// Flux field and corresponding velocity field. Fluxes on changed
// faces get recalculated by interpolating the velocity. Use 'none'
// on surfaceScalarFields that do not need to be reinterpolated.
correctFluxes
(
    (phi none)
    (nHatf none)
    (rhoPhi none)
    (alphaPhi0.water none)
    (ghf none)
);

// Write the refinement level as a volScalarField
dumpLevel       true;


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

/*--------------------------------*- C++ -*----------------------------------*\
| =========                 |                                                 |
| \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox           |
|  \\    /   O peration     | Version:  2212                                     |
|   \\  /    A nd           | Web:      www.OpenFOAM.org                      |
|    \\/     M anipulation  |                                                 |
\*---------------------------------------------------------------------------*/
FoamFile
{
    version     2.0;
    format      ascii;
    class       dictionary;
    object      blockMeshDict;
}
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //

convertToMeters 1;


hN  1.01e-4;

L   #calc "100*$hN";
D   #calc "1.0*$hN";
H   #calc "3.0*$hN";
z   #calc "M_PI*$L";

nX  100; 
nY  50;
nZ  100;

vertices
(
    (0  0  0) //0 
    ($L 0  0) //1
    ($L $H 0) //2
    (0  $H 0) //3

    (0  0  $z) //4
    ($L 0  $z) //5
    ($L $H $z) //6
    (0  $H $z) //7
);

blocks
(
    hex (0 1 2 3 4 5 6 7) ($nX $nY $nZ) simpleGrading (1 1 1)
);

edges
(
);


boundary
(
    movingWall
    {
        type wall;
        faces
        (
            (0 1 5 4)
        );
    }
    inlet
    {
        type                  cyclicAMI;
        neighbourPatch        outlet;
        transform       translational;
        separationVector ($L 0 0);
        faces
        (
            (0 4 7 3)
        );
    }
    outlet
    {
        type                  cyclicAMI;
        neighbourPatch        inlet;
        transform       translational;
        separationVector (-$L 0 0);
        faces
        (
            (1 5 6 2)
        );
    }
      atmosphere
    {
        type patch;
        faces
        (
            (3 2 6 7)
        );
    }
    front
    {
        type cyclicAMI;
        neighbourPatch        back;
        transform       translational;
        separationVector (0 0 $z);
        faces
        (
            (0 1 2 3)
        );
    }
    back
    {
        type cyclicAMI;
        neighbourPatch        front;
        transform       translational;
        separationVector (0 0 -$z);
        faces
        (
            (4 5 6 7)
        );
    }
);

mergePatchPairs
(
);

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

[Emrys]

网格是需要接近1：1：1加密吗？整个区域尺寸的比例约为1：300：100

[李东岳]

加密之后时间步长变小是必然的。网格变小，为了保证库朗数小，只能减小时间步长

[Emrys]

@李东岳 谢谢李老师回复，可是全场加密下1000w网格跑的比局部加密67w网格快是不是不太合理

[李东岳]

那是不太合理，可能你67万的要发散了