ENH: Added new Curle function object

Calculates the acoustic pressure based on Curle's analogy.

Curle's analogy is implemented as:

    \f[
        p' = 4 \frac{\pi}{c_0}\frac{\vec d}{|\vec d|^2}\frac{d(F)}{d(t)}
    \f]

where
    p'          | Curle's acoustic pressure [Pa] or [Pa (m3/rho)]
    c_0         | Reference speed of sound [m/s]
    \vec d      | Distance vector to observer locations [m]
    F           | Force [N] or [N (m3/rho)]

src/functionObjects/field/Curle/Curle.C

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     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 "Curle.H"
+#include "fvcDdt.H"
+#include "mathematicalConstants.H"
+#include "addToRunTimeSelectionTable.H"
+
+using namespace Foam::constant;
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+    defineTypeNameAndDebug(Curle, 0);
+
+    addToRunTimeSelectionTable
+    (
+        functionObject,
+        Curle,
+        dictionary
+    );
+}
+}
+
+
+// * * * * * * * * * * * * Protected Member Functions  * * * * * * * * * * * //
+
+bool Foam::functionObjects::Curle::calc()
+{
+    if (foundObject<volScalarField>(fieldName_))
+    {
+        // Evaluate pressure force time derivative
+
+        const volScalarField& p = lookupObject<volScalarField>(fieldName_);
+        const volScalarField dpdt(scopedName("dpdt"), fvc::ddt(p));
+        const volScalarField::Boundary& dpdtBf = dpdt.boundaryField();
+        const surfaceVectorField::Boundary& SfBf = mesh_.Sf().boundaryField();
+
+        dimensionedVector dfdt
+        (
+            "0",
+            p.dimensions()*dimArea/dimTime,
+            vector::zero
+        );
+
+        for (auto patchi : patchSet_)
+        {
+            dfdt.value() += sum(dpdtBf[patchi]*SfBf[patchi]);
+        }
+
+        reduce(dfdt.value(), sumOp<vector>());
+
+
+        // Construct and store Curle acoustic pressure
+
+        const volVectorField& C = mesh_.C();
+
+        tmp<volScalarField> tpDash
+        (
+            new volScalarField
+            (
+                IOobject
+                (
+                    resultName_,
+                    mesh_.time().timeName(),
+                    mesh_,
+                    IOobject::NO_READ,
+                    IOobject::NO_WRITE
+                ),
+                mesh_,
+                dimensionedScalar("0", p.dimensions(), 0)
+            )
+        );
+
+        volScalarField& pDash = tpDash.ref();
+        const volVectorField d(scopedName("d"), C - x0_);
+        pDash = 4*mathematical::pi/c0_*(d/magSqr(d) & dfdt);
+
+        return store(resultName_, tpDash);
+    }
+    else
+    {
+        return false;
+    }
+}
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::functionObjects::Curle::Curle
+(
+    const word& name,
+    const Time& runTime,
+    const dictionary& dict
+)
+:
+    fieldExpression(name, runTime, dict, "p"),
+    patchSet_(),
+    x0_("x0", dimLength, vector::zero),
+    c0_("c0", dimVelocity, 0)
+{
+    read(dict);
+
+    setResultName(typeName, fieldName_);
+}
+
+
+// * * * * * * * * * * * * * * * * Destructor  * * * * * * * * * * * * * * * //
+
+Foam::functionObjects::Curle::~Curle()
+{}
+
+
+// * * * * * * * * * * * * * * * Member Functions  * * * * * * * * * * * * * //
+
+bool Foam::functionObjects::Curle::read(const dictionary& dict)
+{
+    if (fieldExpression::read(dict))
+    {
+        patchSet_ =
+            mesh_.boundaryMesh().patchSet(wordReList(dict.lookup("patches")));
+
+        if (patchSet_.empty())
+        {
+            WarningInFunction
+                << "No patches defined"
+                << endl;
+
+            return false;
+        }
+
+        // Read the reference speed of sound
+        dict.lookup("c0") >> c0_;
+
+
+        // Set the location of the effective point source to the area-average
+        // of the patch face centres
+        const volVectorField::Boundary& Cbf = mesh_.C().boundaryField();
+        const surfaceScalarField::Boundary& magSfBf =
+            mesh_.magSf().boundaryField();
+
+        x0_.value() = vector::zero;
+        scalar sumMagSf = 0;
+        for (auto patchi : patchSet_)
+        {
+            x0_.value() += sum(Cbf[patchi]*magSfBf[patchi]);
+            sumMagSf += sum(magSfBf[patchi]);
+        }
+
+        reduce(x0_.value(), sumOp<vector>());
+        reduce(sumMagSf, sumOp<scalar>());
+
+        x0_.value() /= sumMagSf + ROOTVSMALL;
+
+        return true;
+    }
+
+    return false;
+}
+
+
+// ************************************************************************* //

src/functionObjects/field/Curle/Curle.H

+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2017 OpenCFD Ltd.
+     \\/     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::Curle
+
+Group
+    grpFieldFunctionObjects
+
+Description
+    Calculates the acoustic pressure based on Curle's analogy.
+
+    Curle's analogy is implemented as:
+
+    \f[
+        p' = 4 \frac{\pi}{c_0}\frac{\vec d}{|\vec d|^2}\frac{d(F)}{d(t)} 
+    \f]
+
+
+    where
+    \vartable
+        p'          | Curle's acoustic pressure [Pa] or [Pa (m3/rho)]
+        c_0         | Reference speed of sound [m/s]
+        \vec d      | Distance vector to observer locations [m]
+        F           | Force [N] or [N (m3/rho)]
+    \endvartable
+
+Note
+    Only the normal-pressure force is included in the force calculation
+
+
+Usage
+    Example of function object specification:
+    \verbatim
+    Curle1
+    {
+        type        Curle;
+        libs        ("libfieldFunctionObjects.so");
+        ...
+        patches     (surface1 surface2);
+        c0          330;
+    }
+    \endverbatim
+
+    Where the entries comprise:
+    \table
+        Property     | Description                  | Required | Default value
+        type         | Type name: Curle             | yes      |
+        field        | Pressure field name          | no       | p
+        result       | Acoustic pressure field name | no       | Curle
+        patches      | Sound generation patch names | yes      | 
+        c0           | Reference speed of sound     | yes      | 
+    \endtable
+
+
+See also
+  - Foam::functionObjects::fieldExpression
+  - Foam::functionObjects::fvMeshFunctionObject
+
+SourceFiles
+    Curle.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef functionObjects_Curle_H
+#define functionObjects_Curle_H
+
+#include "fieldExpression.H"
+#include "dimensionedScalar.H"
+#include "dimensionedVector.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+
+/*---------------------------------------------------------------------------*\
+                            Class Curle Declaration
+\*---------------------------------------------------------------------------*/
+
+class Curle
+:
+    public fieldExpression
+{
+    // Private data
+
+        // Read from dictionary
+
+            //- Patches to integrate forces over
+            labelHashSet patchSet_;
+
+            //- Area-averaged centre of patch faces
+            dimensionedVector x0_;
+
+            //- Reference speed of souund
+            dimensionedScalar c0_;
+
+
+    // Private Member Functions
+
+        //- Disallow default bitwise copy construct
+        Curle(const Curle&) = delete;
+
+        //- Disallow default bitwise assignment
+        void operator=(const Curle&) = delete;
+
+
+protected:
+
+        //- Calculate the acoustic pressure field and return true if successful
+        virtual bool calc();
+
+
+public:
+
+    //- Runtime type information
+    TypeName("Curle");
+
+
+    // Constructors
+
+        //- Construct from Time and dictionary
+        Curle
+        (
+            const word& name,
+            const Time& runTime,
+            const dictionary& dict
+        );
+
+
+    //- Destructor
+    virtual ~Curle();
+
+
+    // Member Functions
+
+        //- Read the Curle data
+        virtual bool read(const dictionary&);
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace functionObjects
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //

src/functionObjects/field/Make/files

@@ -52,6 +52,7 @@ PecletNo/PecletNo.C
 blendingFactor/blendingFactor.C
 pressure/pressure.C
 MachNo/MachNo.C
+Curle/Curle.C
 
 fieldsExpression/fieldsExpression.C
 add/add.C