functionObjects: New function to reconstruct cell velocity from face flux

This is a simple function that provides a convenient way for a user to
call fvc::reconstruct for the purposes of post-processing flux fields;
e.g., to construct a cell velocity from a face flux.

It can be used to generate output during a run by adding the following
settings to a case's controlDict:

    functions
    {
        #includeFunc reconstruct(phi)
    }

Or it can be executed as a postProcessing step by calling:

    postProcess -func "reconstruct(phi)"

etc/caseDicts/postProcessing/fields/reconstruct

@@ -0,0 +1,22 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Version:  dev
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+Description
+    Calculates the reconstruction of a field; e.g., to construct a cell-centred
+    velocity, U, from the face-centred flux, phi.
+
+\*---------------------------------------------------------------------------*/
+
+type            reconstruct;
+libs            ("libfieldFunctionObjects.so");
+
+field           <fieldName>;
+
+executeControl  writeTime;
+writeControl    writeTime;
+
+// ************************************************************************* //

src/functionObjects/field/Make/files

@@ -47,6 +47,7 @@ pressure/pressure.C
 MachNo/MachNo.C
 shearStress/shearStress.C
 totalEnthalpy/totalEnthalpy.C
+reconstruct/reconstruct.C
 
 turbulenceFields/turbulenceFields.C
 yPlus/yPlus.C

src/functionObjects/field/reconstruct/reconstruct.C

@@ -0,0 +1,100 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2022 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+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 "reconstruct.H"
+#include "fvcReconstruct.H"
+#include "addToRunTimeSelectionTable.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+    defineTypeNameAndDebug(reconstruct, 0);
+    addToRunTimeSelectionTable(functionObject, reconstruct, dictionary);
+}
+}
+
+
+// * * * * * * * * * * * * * Private Member Functions  * * * * * * * * * * * //
+
+template<class Type>
+bool Foam::functionObjects::reconstruct::calcReconstruction()
+{
+    typedef GeometricField<Type, fvsPatchField, surfaceMesh> SurfaceFieldType;
+
+    if (foundObject<SurfaceFieldType>(fieldName_))
+    {
+        return store
+        (
+            resultName_,
+            fvc::reconstruct(lookupObject<SurfaceFieldType>(fieldName_)),
+            mesh_.changing() && mesh_.solution().cache(resultName_)
+        );
+    }
+    else
+    {
+        return false;
+    }
+}
+
+
+bool Foam::functionObjects::reconstruct::calc()
+{
+    bool processed = false;
+
+    processed = processed || calcReconstruction<scalar>();
+    processed = processed || calcReconstruction<vector>();
+
+    if (!processed)
+    {
+        cannotFindObject(fieldName_);
+    }
+
+    return processed;
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::functionObjects::reconstruct::reconstruct
+(
+    const word& name,
+    const Time& runTime,
+    const dictionary& dict
+)
+:
+    fieldExpression(name, runTime, dict, typeName)
+{}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::functionObjects::reconstruct::~reconstruct()
+{}
+
+
+// ************************************************************************* //

src/functionObjects/field/reconstruct/reconstruct.H

@@ -0,0 +1,102 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     | Website:  https://openfoam.org
+    \\  /    A nd           | Copyright (C) 2022 OpenFOAM Foundation
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+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::reconstruct
+
+Description
+    Calculates the reconstruction of a field; e.g., to construct a cell-centred
+    velocity, U, from the face-centred flux, phi. The operation is limited to
+    scalar and vector surface fields, and the output is a volume vector or
+    tensor field.
+
+See also
+    Foam::functionObjects::fvMeshFunctionObject
+
+SourceFiles
+    reconstruct.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef functionObjects_reconstruct_H
+#define functionObjects_reconstruct_H
+
+#include "fieldExpression.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+
+/*---------------------------------------------------------------------------*\
+                            Class reconstruct Declaration
+\*---------------------------------------------------------------------------*/
+
+class reconstruct
+:
+    public fieldExpression
+{
+    // Private Member Functions
+
+        //- Calculate the magnitude of the field and register the result
+        template<class Type>
+        inline bool calcReconstruction();
+
+        //- Calculate the reconstruction field and return true if successful
+        virtual bool calc();
+
+
+public:
+
+    //- Runtime type information
+    TypeName("reconstruct");
+
+
+    // Constructors
+
+        //- Construct from Time and dictionary
+        reconstruct
+        (
+            const word& name,
+            const Time& runTime,
+            const dictionary& dict
+        );
+
+
+    //- Destructor
+    virtual ~reconstruct();
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace functionObjects
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

test/postProcessing/channel/system/controlDict

@@ -118,6 +118,8 @@ fieldsFunctions
 
     #includeFunc randomise(U, magPerturbation=0.1)
 
+    #includeFunc reconstruct(phi)
+
     #includeFunc scale(age, scale=0.1)
 
     #includeFunc shearStress