OpenFOAM

OpenFOAM 中的热物理类之接口

本系列来看一下 OpenFOAM 中的热物理类。热物理类比较繁杂，这里先看一下纯物质的热物理模型。本篇先来看看热物理类在求解器中的接口，以2.3.x 版的 twoPhaseEulerFoam 为例。

twoPhaseEulerFoam 中的热物理类的接口在 phaseModel 类中声明：

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//- Thermophysical properties
autoPtr<rhoThermo> thermo_;

thermo_(rhoThermo::New(fluid.mesh(), name_))

可见，接口是 rhoThermo 类的指针。

接着看 rhoThermo 类的 New 函数。

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//- Selector
static autoPtr<rhoThermo> New
(
    const fvMesh&,
    const word& phaseName=word::null
);
    
Foam::autoPtr<Foam::rhoThermo> Foam::rhoThermo::New
(
    const fvMesh& mesh,
    const word& phaseName
)
{
    return basicThermo::New<rhoThermo>(mesh, phaseName);
}

这里调用的是 basicThermo 类的 New 函数。 这里先提一下继承关系，后面再细说：rhoThermo 类继承自 fluidThermo ， fluidThermo 类继承自 basicThermo。

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//- Generic New for each of the related thermodynamics packages
// basicThermo.C

template<class Thermo>
static autoPtr<Thermo> New
(
    const fvMesh&,
    const word& phaseName=word::null
);

template<class Thermo>
Foam::autoPtr<Thermo> Foam::basicThermo::New
(
    const fvMesh& mesh,
    const word& phaseName
)
{
    IOdictionary thermoDict
    (
        IOobject
        (
            phasePropertyName(dictName, phaseName),
            mesh.time().constant(),
            mesh,
            IOobject::MUST_READ_IF_MODIFIED,
            IOobject::NO_WRITE,
            false
        )
    );

    typename Thermo::fvMeshConstructorTable::iterator cstrIter =
        lookupThermo<Thermo, typename Thermo::fvMeshConstructorTable>
        (
            thermoDict,
            Thermo::fvMeshConstructorTablePtr_
        );

    return autoPtr<Thermo>(cstrIter()(mesh, phaseName));
}

根据 RTS 机制的惯例， New 函数的功能是模型选择(selector)，即根据用户指定的关键字来选择对应的模型。 New 函数中先定义了一个 IOdictionary 类的对象， thermoDict，这个对象对应的正是热物理类的配置文件 thermophysicalProperties。New 函数里调用了 lookupThermo 函数，这个函数是关键：

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// basicThermoTemplates.C
template<class Thermo, class Table>
typename Table::iterator Foam::basicThermo::lookupThermo
(
    const dictionary& thermoDict,
    Table* tablePtr
)
{
    word thermoTypeName;

    if (thermoDict.isDict("thermoType"))
    {
        const dictionary& thermoTypeDict(thermoDict.subDict("thermoType"));

        Info<< "Selecting thermodynamics package " << thermoTypeDict << endl;

        const int nCmpt = 7;
        const char* cmptNames[nCmpt] =
        {
            "type",
            "mixture",
            "transport",
            "thermo",
            "equationOfState",
            "specie",
            "energy"
        };

        // Construct the name of the thermo package from the components
        thermoTypeName =
            word(thermoTypeDict.lookup("type")) + '<'
          + word(thermoTypeDict.lookup("mixture")) + '<'
          + word(thermoTypeDict.lookup("transport")) + '<'
          + word(thermoTypeDict.lookup("thermo")) + '<'
          + word(thermoTypeDict.lookup("equationOfState")) + '<'
          + word(thermoTypeDict.lookup("specie")) + ">>,"
          + word(thermoTypeDict.lookup("energy")) + ">>>";

        // Lookup the thermo package
        typename Table::iterator cstrIter = tablePtr->find(thermoTypeName);

        // Print error message if package not found in the table
        if (cstrIter == tablePtr->end())
        {
            FatalErrorIn(Thermo::typeName + "::New")
                << "Unknown " << Thermo::typeName << " type " << nl
                << "thermoType" << thermoTypeDict << nl << nl
                << "Valid " << Thermo::typeName << " types are:" << nl << nl;

            // Get the list of all the suitable thermo packages available
            wordList validThermoTypeNames
            (
                tablePtr->sortedToc()
            );

            // Build a table of the thermo packages constituent parts
            // Note: row-0 contains the names of constituent parts
            List<wordList> validThermoTypeNameCmpts
            (
                validThermoTypeNames.size() + 1
            );

            validThermoTypeNameCmpts[0].setSize(nCmpt);
            forAll(validThermoTypeNameCmpts[0], j)
            {
                validThermoTypeNameCmpts[0][j] = cmptNames[j];
            }

            // Split the thermo package names into their constituent parts
            forAll(validThermoTypeNames, i)
            {
                validThermoTypeNameCmpts[i+1] =
                    Thermo::splitThermoName(validThermoTypeNames[i], nCmpt);
            }

            // Print the table of available packages
            // in terms of their constituent parts
            printTable(validThermoTypeNameCmpts, FatalError);

            FatalError<< exit(FatalError);
        }

        return cstrIter;
    }
    else
    {
        thermoTypeName = word(thermoDict.lookup("thermoType"));

        Info<< "Selecting thermodynamics package " << thermoTypeName << endl;

        typename Table::iterator cstrIter = tablePtr->find(thermoTypeName);

        if (cstrIter == tablePtr->end())
        {
            FatalErrorIn(Thermo::typeName + "::New")
                << "Unknown " << Thermo::typeName << " type "
                << thermoTypeName << nl << nl
                << "Valid " << Thermo::typeName << " types are:" << nl
                << tablePtr->sortedToc() << nl
                << exit(FatalError);
        }

        return cstrIter;
    }
}

可见， loopupThermo 分两种情况处理，一种是 thermophysicalProperties 文件里有一个名为 thermoType 的 subdict，例如

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thermoType
{
    type            heRhoThermo;
    mixture         pureMixture;
    transport       const;
    thermo          hConst;
    equationOfState perfectGas;
    specie          specie;
    energy          sensibleInternalEnergy;
}

这种情况下， subdict 里的 7 个关键字将逐一读入，最终将合并起来，得到一个字符串，并赋值给 thermoTypeName
以上面的那种情况为例，最终得到的thermoTypeName 为

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heRhoThermo<pureMixture<const<hConst<perfectGas<specie>>,sensibleInternalEnergy>>>

然后，根据这个关键词，从 hashTable 中找到对应的元素。如果找不到对应的，则报错，并输出所有可选的方案(由 splitThermoName 和 printTable 两个函数完成，细节这里暂且不表)。

另一种情况，直接从 thermophysicalProperties 读取 thermoType 对应的字符串并赋值给 thermoTypeName，然后据此来从 hashTable 中找到对应的元素。

OpenFOAM 自带的算例中，thermophysicalProperties 文件绝大部分采用前一种方式，因为更直观。后一种方式我在 OpenFOAM-2.3.x 版中只找到一个例子：tutorials/mesh/foamyQuadMesh/OpenCFD/constant/thermophysicalProperties

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thermoType      hePsiThermo<pureMixture<const<hConst<perfectGas<specie>>,sensibleEnthalpy>>>;

至此，大致就知道热物理类的接口定义是怎么回事了。但是，这个存储了可选模型的 hashTable 里有哪些内容，又是怎么构建起来的，还有待进一步深入探索。另外，从 thermoType 对应的字符串的样式，能猜到最终热物理类的接口 thermo_ 指向的可能是类似 heRhoThermo 类的对象，而且这些类多半是模板类，并有着复杂的继承派生关系，这部分也还有待深入探索。