ENH: Function objects - added new 'multiply' function object

Multiplies a given list of (at least two or more) fields and outputs the
result into a new field.

    fieldResult = field1 * field2 * ... * fieldN

Minimal example by using \c system/controlDict.functions:

    multiply1
    {
        // Mandatory entries (unmodifiable)
        type    multiply;
        libs    (fieldFunctionObjects);

        // Mandatory (inherited) entry (runtime modifiable)
        fields  (<field1> <field2> ... <fieldN>);

        ...
    }

src/functionObjects/field/Make/files

@@ -85,6 +85,7 @@ pow/pow.C
 fieldsExpression/fieldsExpression.C
 add/add.C
 subtract/subtract.C
+multiply/multiply.C
 
 turbulenceFields/turbulenceFields.C
 yPlus/yPlus.C

src/functionObjects/field/multiply/multiply.C

@@ -0,0 +1,89 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+#include "multiply.H"
+#include "addToRunTimeSelectionTable.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+    defineTypeNameAndDebug(multiply, 0);
+    addToRunTimeSelectionTable(functionObject, multiply, dictionary);
+}
+}
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::functionObjects::multiply::multiply
+(
+    const word& name,
+    const Time& runTime,
+    const dictionary& dict
+)
+:
+    fieldsExpression(name, runTime, dict)
+{
+    setResultName("multiply");
+}
+
+
+bool Foam::functionObjects::multiply::calc()
+{
+    bool processed = false;
+
+    Log << type() << ' ' << name() <<  " execute:" << nl;
+
+    forAll(fieldNames_, i)
+    {
+        processed = false;
+
+        if (i == 0)
+        {
+            initialiseResult<scalar>(fieldNames_[i]);
+            initialiseResult<vector>(fieldNames_[i]);
+            initialiseResult<sphericalTensor>(fieldNames_[i]);
+            initialiseResult<symmTensor>(fieldNames_[i]);
+            initialiseResult<tensor>(fieldNames_[i]);
+        }
+        else
+        {
+            multiplyResult<scalar>(fieldNames_[i], processed);
+            multiplyResult<vector>(fieldNames_[i], processed);
+            multiplyResult<sphericalTensor>(fieldNames_[i], processed);
+            multiplyResult<symmTensor>(fieldNames_[i], processed);
+            multiplyResult<tensor>(fieldNames_[i], processed);
+        }
+    }
+
+    return processed;
+}
+
+
+// ************************************************************************* //

src/functionObjects/field/multiply/multiply.H

@@ -0,0 +1,203 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+Class
+    Foam::functionObjects::multiply
+
+Group
+    grpFieldFunctionObjects
+
+Description
+    Multiplies a given list of (at least two or more) fields and outputs the
+    result into a new field.
+
+    \verbatim
+        fieldResult = field1 * field2 * ... * fieldN
+    \endverbatim
+
+    Operands:
+    \table
+      Operand      | Type                          | Location
+      input        | vol\<Type\>Field(s) <!--
+               --> |$FOAM_CASE/\<time\>/\<inpField\>s
+      output field | vol\<Type\>Field    <!--
+               --> | $FOAM_CASE/\<time\>/\<outField\>
+    \endtable
+
+    where \c \<Type\>=Scalar/Vector/SphericalTensor/SymmTensor/Tensor.
+
+Usage
+    Minimal example by using \c system/controlDict.functions:
+    \verbatim
+    multiply1
+    {
+        // Mandatory entries (unmodifiable)
+        type    multiply;
+        libs    (fieldFunctionObjects);
+
+        // Mandatory (inherited) entry (runtime modifiable)
+        fields  (<field1> <field2> ... <fieldN>);
+
+        // Optional (inherited) entries
+        ...
+    }
+    \endverbatim
+
+    where the entries mean:
+    \table
+      Property     | Description                        | Type | Reqd | Dflt
+      type         | Type name: multiply                | word | yes | -
+      libs         | Library name: fieldFunctionObjects | word | yes | -
+      fields       | Names of the operand fields        | wordList | yes | -
+    \endtable
+
+    The inherited entries are elaborated in:
+     - \link functionObject.H \endlink
+     - \link fieldsExpression.H \endlink
+
+See also
+    - Foam::functionObject
+    - Foam::functionObjects::fieldsExpression
+    - Foam::functionObjects::fvMeshFunctionObject
+
+SourceFiles
+    multiply.C
+    multiplyTemplates.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef functionObjects_multiply_H
+#define functionObjects_multiply_H
+
+#include "fieldsExpression.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+
+/*---------------------------------------------------------------------------*\
+                          Class multiply Declaration
+\*---------------------------------------------------------------------------*/
+
+class multiply
+:
+    public fieldsExpression
+{
+    //- Helper struct to define valid operations
+    template<class Type1, class Type2>
+    struct is_valid_op
+    {
+        static constexpr bool value =
+            (pTraits<Type1>::rank == 0 || pTraits<Type2>::rank == 0)
+         || (pTraits<Type1>::rank == 1 && pTraits<Type2>::rank == 1);
+    };
+
+
+    // Private Member Functions
+
+        template<class Type>
+        bool initialiseResult(const word& fieldName);
+
+        template<class Type>
+        bool multiplyResult(const word& fieldName, bool& processed);
+
+        template<class Type1, class Type2>
+        typename std::enable_if
+        <
+            is_valid_op<Type1, Type2>::value, bool
+        >::type
+        multiplyFieldType
+        (
+            GeometricField<Type1, fvPatchField, volMesh>& result,
+            const word& fieldName,
+            bool& processed
+        );
+
+        template<class Type1, class Type2>
+        typename std::enable_if
+        <
+            !is_valid_op<Type1, Type2>::value, bool
+        >::type
+        multiplyFieldType
+        (
+            GeometricField<Type1, fvPatchField, volMesh>& result,
+            const word& fieldName,
+            bool& processed
+        );
+
+        //- Multiply the list of fields and return true if successful
+        virtual bool calc();
+
+
+public:
+
+    friend class fieldsExpression;
+
+
+    //- Runtime type information
+    TypeName("multiply");
+
+
+    // Constructors
+
+        //- Construct from Time and dictionary
+        multiply
+        (
+            const word& name,
+            const Time& runTime,
+            const dictionary& dict
+        );
+
+        //- No copy construct
+        multiply(const multiply&) = delete;
+
+        //- No copy assignment
+        void operator=(const multiply&) = delete;
+
+
+    //- Destructor
+    virtual ~multiply() = default;
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace functionObjects
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#ifdef NoRepository
+    #include "multiplyTemplates.C"
+#endif
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

src/functionObjects/field/multiply/multiplyTemplates.C

@@ -0,0 +1,156 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2020 OpenCFD Ltd.
+-------------------------------------------------------------------------------
+License
+    This file is part of OpenFOAM.
+
+    OpenFOAM is free software: you can redistribute it and/or modify it
+    under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    OpenFOAM is distributed in the hope that it will be useful, but WITHOUT
+    ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+    for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with OpenFOAM.  If not, see <http://www.gnu.org/licenses/>.
+
+\*---------------------------------------------------------------------------*/
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+template<class Type>
+bool Foam::functionObjects::multiply::initialiseResult(const word& fieldName)
+{
+    typedef GeometricField<Type, fvPatchField, volMesh> volFieldType;
+
+    auto* fieldPtr = mesh_.cfindObject<volFieldType>(fieldName);
+
+    if (fieldPtr)
+    {
+        auto* resultFieldPtr = mesh_.getObjectPtr<regIOobject>(resultName_);
+
+        if (resultFieldPtr)
+        {
+            resultFieldPtr->checkOut();
+        }
+
+        Log << "    Initialising "
+            << resultName_ << " to " << fieldPtr->name() << endl;
+
+        return store(resultName_, tmp<volFieldType>::New(*fieldPtr));
+    }
+
+    return false;
+}
+
+
+template<class Type>
+bool Foam::functionObjects::multiply::multiplyResult
+(
+    const word& fieldName,
+    bool& processed
+)
+{
+    typedef GeometricField<Type, fvPatchField, volMesh> volFieldType;
+
+    auto* resultFieldPtr = mesh_.getObjectPtr<volFieldType>(resultName_);
+
+    if (resultFieldPtr)
+    {
+        multiplyFieldType<Type, scalar>(*resultFieldPtr, fieldName, processed);
+        multiplyFieldType<Type, vector>(*resultFieldPtr, fieldName, processed);
+        multiplyFieldType<Type, sphericalTensor>
+        (
+            *resultFieldPtr,
+            fieldName,
+            processed
+        );
+        multiplyFieldType<Type, symmTensor>
+        (
+            *resultFieldPtr,
+            fieldName,
+            processed
+        );
+        multiplyFieldType<Type, tensor>(*resultFieldPtr, fieldName, processed);
+    }
+
+    return processed;
+}
+
+
+template<class Type1, class Type2>
+typename std::enable_if
+<
+    Foam::functionObjects::multiply::is_valid_op<Type1, Type2>::value, bool
+>::type
+Foam::functionObjects::multiply::multiplyFieldType
+(
+    GeometricField<Type1, fvPatchField, volMesh>& result,
+    const word& fieldName,
+    bool& processed
+)
+{
+    if (processed) return processed;
+
+    typedef GeometricField<Type2, fvPatchField, volMesh> volFieldType;
+
+    auto* fieldPtr = mesh_.cfindObject<volFieldType>(fieldName);
+
+    if (fieldPtr)
+    {
+        Log << "    Performing " << result.name() << " * " << fieldPtr->name()
+            << endl;
+
+        auto newResult(result*(*fieldPtr));
+        result.checkOut();
+
+        store(resultName_, newResult);
+
+        processed = true;
+    }
+
+    return processed;
+}
+
+
+template<class Type1, class Type2>
+typename std::enable_if
+<
+    !Foam::functionObjects::multiply::is_valid_op<Type1, Type2>::value, bool
+>::type
+Foam::functionObjects::multiply::multiplyFieldType
+(
+    GeometricField<Type1, fvPatchField, volMesh>& result,
+    const word& fieldName,
+    bool& processed
+)
+{
+    if (processed) return processed;
+
+    typedef GeometricField<Type2, fvPatchField, volMesh> volFieldType;
+
+    auto* fieldPtr = mesh_.cfindObject<volFieldType>(fieldName);
+
+    if (fieldPtr)
+    {
+        Info<< "    Unsupported operation for "
+            << result.name() << '(' << pTraits<Type1>::typeName << ')'
+            << " * "
+            << fieldPtr->name() << '(' << pTraits<Type2>::typeName << ')'
+            << endl;
+    }
+
+    return processed;
+}
+
+
+// ************************************************************************* //