ENH: overset: Initial release of overset capability.

Adds overset discretisation to selected physics:
- diffusion : overLaplacianDyMFoam
- incompressible steady : overSimpleFoam
- incompressible transient : overPimpleDyMFoam
- compressible transient: overRhoPimpleDyMFoam
- two-phase VOF: overInterDyMFoam

The overset method chosen is a parallel, fully implicit implementation
whereby the interpolation (from donor to acceptor) is inserted as an
adapted discretisation on the donor cells, such that the resulting matrix
can be solved using the standard linear solvers.

Above solvers come with a set of tutorials, showing how to create and set-up
simple simulations from scratch.

applications/solvers/basic/laplacianFoam/overLaplacianDyMFoam/Make/files

@@ -0,0 +1,3 @@
+laplacianDyMFoam.C
+
+EXE = $(FOAM_APPBIN)/overLaplacianDyMFoam

applications/solvers/basic/laplacianFoam/overLaplacianDyMFoam/Make/options

@@ -0,0 +1,8 @@
+EXE_INC = \
+    -I$(LIB_SRC)/finiteVolume/lnInclude \
+    -I$(LIB_SRC)/dynamicFvMesh/lnInclude \
+    -I$(LIB_SRC)/overset/lnInclude \
+    -I$(LIB_SRC)/meshTools/lnInclude
+
+EXE_LIBS = \
+    -loverset

applications/solvers/basic/laplacianFoam/overLaplacianDyMFoam/createFields.H

@@ -0,0 +1,53 @@
+    Info<< "Reading field T\n" << endl;
+
+    volScalarField T
+    (
+        IOobject
+        (
+            "T",
+            runTime.timeName(),
+            mesh,
+            IOobject::MUST_READ,
+            IOobject::AUTO_WRITE
+        ),
+        mesh
+    );
+
+    // Add overset specific interpolations
+    {
+        dictionary oversetDict;
+        oversetDict.add("T", true);
+
+        const_cast<dictionary&>
+        (
+            mesh.schemesDict()
+        ).add
+        (
+            "oversetInterpolationRequired",
+            oversetDict,
+            true
+        );
+    }
+
+
+    Info<< "Reading transportProperties\n" << endl;
+
+    IOdictionary transportProperties
+    (
+        IOobject
+        (
+            "transportProperties",
+            runTime.constant(),
+            mesh,
+            IOobject::MUST_READ_IF_MODIFIED,
+            IOobject::NO_WRITE
+        )
+    );
+
+
+    Info<< "Reading diffusivity DT\n" << endl;
+
+    dimensionedScalar DT
+    (
+        transportProperties.lookup("DT")
+    );

applications/solvers/basic/laplacianFoam/overLaplacianDyMFoam/laplacianDyMFoam.C

@@ -0,0 +1,110 @@
+/*---------------------------------------------------------------------------*\
+  =========                 |
+  \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
+   \\    /   O peration     |
+    \\  /    A nd           | Copyright (C) 2011-2015 OpenFOAM Foundation
+     \\/     M anipulation  | Copyright (C) 2016-2017 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/>.
+
+Application
+    laplacianFoam
+
+Group
+    grpBasicSolvers
+
+Description
+    Laplace equation solver for a scalar quantity.
+
+    \heading Solver details
+    The solver is applicable to, e.g. for thermal diffusion in a solid.  The
+    equation is given by:
+
+    \f[
+        \ddt{T}  = \div \left( D_T \grad T \right)
+    \f]
+
+    Where:
+    \vartable
+        T     | Scalar field which is solved for, e.g. temperature
+        D_T   | Diffusion coefficient
+    \endvartable
+
+    \heading Required fields
+    \plaintable
+        T     | Scalar field which is solved for, e.g. temperature
+    \endplaintable
+
+\*---------------------------------------------------------------------------*/
+
+#include "fvCFD.H"
+#include "fvOptions.H"
+#include "simpleControl.H"
+#include "dynamicFvMesh.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+int main(int argc, char *argv[])
+{
+    #include "setRootCase.H"
+
+    #include "createTime.H"
+    #include "createNamedDynamicFvMesh.H"
+
+    simpleControl simple(mesh);
+
+    #include "createFields.H"
+    #include "createFvOptions.H"
+
+    // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+    Info<< "\nCalculating temperature distribution\n" << endl;
+
+    while (simple.loop())
+    {
+        Info<< "Time = " << runTime.timeName() << nl << endl;
+
+        mesh.update();
+
+        while (simple.correctNonOrthogonal())
+        {
+            fvScalarMatrix TEqn
+            (
+                fvm::ddt(T) - fvm::laplacian(DT, T)
+             ==
+                fvOptions(T)
+            );
+
+            fvOptions.constrain(TEqn);
+            TEqn.solve();
+            fvOptions.correct(T);
+        }
+
+        #include "write.H"
+
+        Info<< "ExecutionTime = " << runTime.elapsedCpuTime() << " s"
+            << "  ClockTime = " << runTime.elapsedClockTime() << " s"
+            << nl << endl;
+    }
+
+    Info<< "End\n" << endl;
+
+    return 0;
+}
+
+
+// ************************************************************************* //

applications/solvers/basic/laplacianFoam/overLaplacianDyMFoam/write.H

@@ -0,0 +1,46 @@
+    if (runTime.outputTime())
+    {
+        volVectorField gradT(fvc::grad(T));
+
+        volScalarField gradTx
+        (
+            IOobject
+            (
+                "gradTx",
+                runTime.timeName(),
+                mesh,
+                IOobject::NO_READ,
+                IOobject::AUTO_WRITE
+            ),
+            gradT.component(vector::X)
+        );
+
+        volScalarField gradTy
+        (
+            IOobject
+            (
+                "gradTy",
+                runTime.timeName(),
+                mesh,
+                IOobject::NO_READ,
+                IOobject::AUTO_WRITE
+            ),
+            gradT.component(vector::Y)
+        );
+
+        volScalarField gradTz
+        (
+            IOobject
+            (
+                "gradTz",
+                runTime.timeName(),
+                mesh,
+                IOobject::NO_READ,
+                IOobject::AUTO_WRITE
+            ),
+            gradT.component(vector::Z)
+        );
+
+
+        runTime.write();
+    }