在使用codedFixedValue边界条件时，如何获得网格中心坐标？

[知白]

大家好，我在学习一个shotSleeveModeling的动网格案例，几何模型如下，运动边界为movingWalls；

我采用codedFixedValue边界条件，实现了movingWalls边界的往复运动，pointDisplacement和dynamicMeshDict文件的部分内容如下：

//pointDisplacement
boundaryField
{

    "(outlet|fixedWalls)"
    {
        type       fixedValue;
        value     uniform (0 0 0);
    }

    movingWalls
    {
        type    codedFixedValue;
        value   uniform (0 0 0);
        name    name_of_BC;

        code
        #{
            //const fvPatch & boundaryPatch = patch();
            //const Patch & boundaryPatch = patch();
            //const vectorField & Cf = boundaryPatch.Cf(); 

            vectorField & field = *this;
            scalar U_0 = 0.1, p_r = 0.03;
            scalar t = this->db().time().value();

            forAll(field, faceI)
            {
                //const scalar x = boundaryPatch.Cf()[faceI][0];
                //const scalar y = boundaryPatch.Cf()[faceI][1];
                //const scalar z = boundaryPatch.Cf()[faceI][2];

                field[faceI].x() = 0;
                field[faceI].y() = 0;
                field[faceI].z() = U_0*sin(t);
                //field[faceI].z() = U_0*sin(t)*pow(field[faceI].y(),2)/(p_r*p_r);
            }
        #};
    }
    slipWalls
    {

        type            calculated;
    }

    frontAndBack
    {
        //type            empty;
        type            calculated;
    }
}

//dynamicMeshDict
dynamicFvMesh       dynamicMotionSolverFvMesh; 
motionSolverLibs ( "libfvMotionSolvers.so" );
motionSolver          displacementLayeredMotion;
cellZone movingCells;
displacementLayeredMotionCoeffs
{
    regions
    {
        movingCells
        {
            interpolationScheme linear;
            boundaryField
            {
                movingFaces { type follow; }
                boundaryMovingFixed { type  fixedValue; value uniform (0 0 0); }
            }
        }
    }
}

movingWalls边界的往复运动如下图所示：

在实现往复运动的基础上，我想让movingWalls沿y轴方向从中间到两边的网格运动速度递减，呈一个抛物线型，因此我需要获得网格中心坐标；

首先，我在pointDisplacement->movingWalls->code#{ #}中增加如下语句，会报错：

const fvPatch & boundaryPatch = patch();

不过按照提示将上述语句中的fvPatch改成Patch，就可以解决错误了。

但是当我在pointDisplacement->movingWalls->code#{ #}中再增加如下语句，用来获得网格中心坐标时，也会报错：

const vectorField & Cf = boundaryPatch.Cf(); //网格中心

报错内容为：
/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement.boundaryField.movingWalls:40:52: error: ‘const Patch’ {aka ‘const class Foam::pointPatch’} has no member named ‘Cf’

我用了OpenFOAM9和OpenFOAM v2112，都会出错。按照提示，应该是Patch下面没有Cf这个成员，但是我看了很多教程获取网格坐标都是用的Cf。我卡在这很久了，都不知道要怎么修改，希望有知道的大神能指导下，多谢！！！

[李东岳]

mesh.Cf()是带边界场的，这个含有边界的信息，应该是这样：

mesh.Cf().boundaryField()[你的patch编号];

[知白]

@李东岳 李老师好！
OpenFOAM我刚开始学，所以不是很懂，不知道您说的是不是这样使用，可以获得网格x方向的坐标：

 forAll(field, faceI)
{
      const scalar x = mesh.Cf().boundaryField()[faceI][0];

       field[faceI].x() = 0;
       field[faceI].y() = 0;
       field[faceI].z() = U_0*sin(t);
 }

在这样使用时会报错：
error: ‘mesh’ was not declared in this scope

请问这是为什么。

[李东岳]

@知白 你这一行代码可以在求解器层面写。你要是在src的库里面写，你要加个类似这种：

const fvMesh& mesh = U.mesh();

[知白]

@李东岳 李老师您意思是要使用下面代码，需要重新编译求解器，不能只在pointDisplacement里直接修改边界条件吗？

 forAll(field, faceI)
{
      const scalar x = mesh.Cf().boundaryField()[faceI][0];

       field[faceI].x() = 0;
       field[faceI].y() = 0;
       field[faceI].z() = U_0*sin(t);
 }

我看教程里，只是修改了边界条件，没有重新编译求解器:

[李东岳]

你要在边界条件里面写么，那这样：

const fvPatch& boundaryPatch = patch();
const fvBoundaryMesh& boundaryMesh = boundaryPatch.boundaryMesh();
const fvMesh& mesh = boundaryMesh.mesh();

这样可以调用mesh

[知白]

@李东岳 请问李老师，codedFixedValue边界条件在U文件和pointDisplacement文件中获得网格坐标的方法是不是不通用，同样的代码，如：

        type    codedFixedValue;
        value   uniform (0 0 0);
        name    name_of_BC;
        code
        #{
            const Patch& boundaryPatch = patch();
            const vectorField& Cf = patch().Cf();       
        #};

在U文件里可以使用，在pointDisplacement文件里就会出错。

出错内容如下：

Create time

Create mesh for time = 0

Selecting dynamicFvMesh dynamicMotionSolverFvMesh
Selecting motion solver: displacementLayeredMotion
Using dynamicCode for codedFixedValue name_of_BC at line 32 in "/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls"
Creating new library in "dynamicCode/name_of_BC/platforms/linux64GccDPInt32Opt/lib/libname_of_BC_2749dd0d9becc7c4794a34f8159e9b4cbe66efce.so"
"/home/dyfluid/OpenFOAM/OpenFOAM-9/etc/codeTemplates/dynamicCode/codedFixedValuePointPatchFieldTemplate.C" "/mnt/hgfs/share/shotSleeveModeling3/dynamicCode/name_of_BC/codedFixedValuePointPatchFieldTemplate.C"
"/home/dyfluid/OpenFOAM/OpenFOAM-9/etc/codeTemplates/dynamicCode/codedFixedValuePointPatchFieldTemplate.H" "/mnt/hgfs/share/shotSleeveModeling3/dynamicCode/name_of_BC/codedFixedValuePointPatchFieldTemplate.H"
Invoking "wmake -s libso /mnt/hgfs/share/shotSleeveModeling3/dynamicCode/name_of_BC"
wmake libso /mnt/hgfs/share/shotSleeveModeling3/dynamicCode/name_of_BC
    ln: ./lnInclude
ln: failed to create symbolic link './codedFixedValuePointPatchFieldTemplate.C': Operation not supported
ln: failed to create symbolic link './codedFixedValuePointPatchFieldTemplate.H': Operation not supported
    wmkdep: codedFixedValuePointPatchFieldTemplate.C
    Ctoo: codedFixedValuePointPatchFieldTemplate.C
/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls: In member function ‘virtual void Foam::name_of_BCFixedValuePointPatchVectorField::updateCoeffs()’:
/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls:39:45: error: ‘const class Foam::pointPatch’ has no member named ‘Cf’
/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls:37:14: warning: unused variable ‘boundaryPatch’ [-Wunused-variable]
/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls:39:32: warning: unused variable ‘Cf’ [-Wunused-variable]
make: *** [/home/dyfluid/OpenFOAM/OpenFOAM-9/wmake/rules/General/transform:26: Make/linux64GccDPInt32Opt/codedFixedValuePointPatchFieldTemplate.o] Error 1


--> FOAM FATAL IO ERROR: 
Failed wmake "dynamicCode/name_of_BC/platforms/linux64GccDPInt32Opt/lib/libname_of_BC_2749dd0d9becc7c4794a34f8159e9b4cbe66efce.so"


file: /mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls from line 32 to line 36.

    From function void Foam::codedBase::createLibrary(Foam::dynamicCode&, const Foam::dynamicCodeContext&) const
    in file db/dynamicLibrary/codedBase/codedBase.C at line 209.

FOAM exiting

其中最关键的感觉是这几处：

ln: failed to create symbolic link './codedFixedValuePointPatchFieldTemplate.C': Operation not supported
ln: failed to create symbolic link './codedFixedValuePointPatchFieldTemplate.H': Operation not supported

/mnt/hgfs/share/shotSleeveModeling3/0/pointDisplacement/boundaryField/movingWalls:39:45: error: ‘const class Foam::pointPatch’ has no member named ‘Cf’

在U文件使用上述代码，只会出现第一处提示，不会出现第二处错误。

[Z.Weng]

@知白

const fvMesh& mesh = refCast<const fvMesh>(this->db());

赋值建议采用

operator==(field);

具体可以参考codedFixedValuePointPatchField.H的注释

Example:

movingWall
{
    type            codedFixedValue;
    value           uniform 0;
    name    rampedFixedValue;   // name of generated bc

    code
    #{
        operator==
        (
            vector(0,0,1)
            *min(10, 0.1*this->db().time().value())
        );
    #};

    // codeInclude
    //#{
    //    #include "fvCFD.H"
    //#};

    // codeOptions
    //#{
    //    -I$(LIB_SRC)/finiteVolume/lnInclude
    //#};
}

[田畔的风]

pointMotionU和pointDisplacement这些控制动网格节点的边界条件文件的数据类型是pointVectorField，对应的patch类是Foam::pointPatch而不是Foam::fvPatch，这应该就是报错的根本原因。

我的思路如下：

// 获取pointPatch的ID，它和相同边界上的fvPatch的ID是一致的
label patchIndex = patch().index();  

// 在objectRegistry随意获取一个存在的物理场
const volScalarField & p
(
    this->db().objectRegistry::lookupObject<volScalarField>("p");
);

// 从上述物理场中访问fvMesh中的体心/面心场
const vectorField& Cfp = p.mesh().Cf().boundaryField()[patchIndex];