CONT: Addition of compressibleIsoInterFOam and PLIC

1) Implementation of the compressibleIsoInterFOam solver
   2) Implementation of a new PLIC interpolation scheme.
   3) New tutorials associated with the solvers

This implementation was carried out by Henning Scheufler (DLR) and Johan
Roenby (DHI), following :

\verbatim

Henning Scheufler, Johan Roenby,
Accurate and efficient surface reconstruction from volume fraction data
on general meshes, Journal of Computational Physics, 2019, doi
10.1016/j.jcp.2019.01.009

\endverbatim

The integration of the code was carried out by Andy Heather and Sergio
Ferraris from OpenCFD Ltd.

applications/utilities/preProcessing/setAlphaField/alphaFieldFunctions/implicitFunctions/plane/planeImplicitFunction.C

@@ -0,0 +1,75 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2020 DLR
+-------------------------------------------------------------------------------
+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 "planeImplicitFunction.H"
+#include "addToRunTimeSelectionTable.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+    namespace implicitFunctions
+    {
+        defineTypeNameAndDebug(planeImplicitFunction, 0);
+        addToRunTimeSelectionTable
+        (
+            implicitFunction,
+            planeImplicitFunction,
+            dict
+        );
+    }
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors  * * * * * * * * * * * * * * //
+
+Foam::implicitFunctions::planeImplicitFunction::planeImplicitFunction
+(
+    const vector& origin,
+    const vector& normal
+)
+:
+    origin_(origin),
+    normal_(normalised(normal))
+{}
+
+
+Foam::implicitFunctions::planeImplicitFunction::planeImplicitFunction
+(
+    const dictionary& dict
+)
+:
+    planeImplicitFunction
+    (
+        dict.get<vector>("origin"),
+        dict.get<vector>("normal")
+    )
+{}
+
+
+// ************************************************************************* //

applications/utilities/preProcessing/setAlphaField/alphaFieldFunctions/implicitFunctions/plane/planeImplicitFunction.H

@@ -0,0 +1,120 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | www.openfoam.com
+     \\/     M anipulation  |
+-------------------------------------------------------------------------------
+    Copyright (C) 2019 OpenCFD Ltd.
+    Copyright (C) 2019-2020 DLR
+-------------------------------------------------------------------------------
+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::implicitFunctions::planeImplicitFunction
+
+Description
+    creates a plane
+
+    Original code supplied by Henning Scheufler, DLR (2019)
+
+SourceFiles
+    planeImplicitFunction.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef implicitFunction_planeImplicitFunction_H
+#define implicitFunction_planeImplicitFunction_H
+
+#include "implicitFunction.H"
+#include "mathematicalConstants.H"
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace implicitFunctions
+{
+
+/*---------------------------------------------------------------------------*\
+                    Class planeImplicitFunction Declaration
+\*---------------------------------------------------------------------------*/
+
+class planeImplicitFunction
+:
+    public implicitFunction
+{
+    // Private Data
+
+        //- Reference point
+        const vector origin_;
+
+        //- Unit-normal vector
+        const vector normal_;
+
+
+public:
+
+    //- Runtime type information
+    TypeName("plane");
+
+
+    // Constructors
+
+        //- Construct from components
+        planeImplicitFunction(const vector& origin, const vector& normal);
+
+        //- Construct from dictionary (used by implicitFunctions)
+        explicit planeImplicitFunction(const dictionary& dict);
+
+
+    //- Destructor
+    virtual ~planeImplicitFunction() = default;
+
+
+    // Member Functions
+
+        virtual scalar value(const vector& p) const
+        {
+            return -normal_ & (origin_ - p);
+        }
+
+        virtual vector grad(const vector& p) const
+        {
+            // normal_ has the length of one
+            return normal_;
+        }
+
+        virtual scalar distanceToSurfaces(const vector& p) const
+        {
+            // normal_ has the length of one
+            return mag((p - origin_) & -normal_);
+        }
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace implicitFunctions
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //