diff --git a/etc/caseDicts/postProcessing/fields/energySpectrum b/etc/caseDicts/postProcessing/fields/energySpectrum
new file mode 100644
index 0000000000000000000000000000000000000000..4df60270faf7a9a2f2de7469183057feaa63d5b8
--- /dev/null
+++ b/etc/caseDicts/postProcessing/fields/energySpectrum
@@ -0,0 +1,19 @@
+/*--------------------------------*- C++ -*----------------------------------*\
+ ========= |
+ \\ / F ield | OpenFOAM: The Open Source CFD Toolbox
+ \\ / O peration |
+ \\ / A nd | Web: www.OpenFOAM.com
+ \\/ M anipulation |
+-------------------------------------------------------------------------------
+Description
+ Calculates the energy spectrum for a box of turbulence
+
+\*---------------------------------------------------------------------------*/
+
+type energySpectrum;
+libs ("librandomProcessesFunctionObjects.so");
+
+executeControl writeTime;
+writeControl writeTime;
+
+// ************************************************************************* //
diff --git a/src/functionObjects/randomProcesses/Allwmake b/src/functionObjects/randomProcesses/Allwmake
new file mode 100755
index 0000000000000000000000000000000000000000..c81ffedf7817dc95192fe7649ba032bf6e7488c9
--- /dev/null
+++ b/src/functionObjects/randomProcesses/Allwmake
@@ -0,0 +1,16 @@
+#!/bin/sh
+cd ${0%/*} || exit 1 # Run from this directory
+targetType=libso # Preferred library type
+. $WM_PROJECT_DIR/wmake/scripts/AllwmakeParseArguments
+. $WM_PROJECT_DIR/wmake/scripts/have_fftw
+
+#------------------------------------------------------------------------------
+
+if have_fftw
+then
+ wmake $targetType
+else
+ echo "==> skip randomProcesses library (no FFTW)"
+fi
+
+#------------------------------------------------------------------------------
diff --git a/src/functionObjects/randomProcesses/Make/files b/src/functionObjects/randomProcesses/Make/files
new file mode 100644
index 0000000000000000000000000000000000000000..e13e8afc998f172001da30bccfe8e7c54013061a
--- /dev/null
+++ b/src/functionObjects/randomProcesses/Make/files
@@ -0,0 +1,3 @@
+energySpectrum/energySpectrum.C
+
+LIB = $(FOAM_LIBBIN)/librandomProcessesFunctionObjects
diff --git a/src/functionObjects/randomProcesses/Make/options b/src/functionObjects/randomProcesses/Make/options
new file mode 100644
index 0000000000000000000000000000000000000000..4c713c968a763f22cc0bbc61b22ea179f8b56466
--- /dev/null
+++ b/src/functionObjects/randomProcesses/Make/options
@@ -0,0 +1,9 @@
+EXE_INC = \
+ -I$(LIB_SRC)/randomProcesses/lnInclude \
+ -I$(LIB_SRC)/finiteVolume/lnInclude \
+ -I$(LIB_SRC)/meshTools/lnInclude
+
+LIB_LIBS = \
+ -lrandomProcesses \
+ -lfiniteVolume \
+ -lmeshTools
diff --git a/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C
new file mode 100644
index 0000000000000000000000000000000000000000..7c19426a6e998906e4f62f40f96cc99f05bce937
--- /dev/null
+++ b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.C
@@ -0,0 +1,263 @@
+/*---------------------------------------------------------------------------*\
+ ========= |
+ \\ / F ield | OpenFOAM: The Open Source CFD Toolbox
+ \\ / O peration |
+ \\ / A nd | Copyright (C) 2018 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 "energySpectrum.H"
+#include "fft.H"
+#include "fvMesh.H"
+#include "boundBox.H"
+#include "OFstream.H"
+#include "mathematicalConstants.H"
+#include "volFields.H"
+#include "addToRunTimeSelectionTable.H"
+
+// * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+ defineTypeNameAndDebug(energySpectrum, 0);
+ addToRunTimeSelectionTable(functionObject, energySpectrum, dictionary);
+}
+}
+
+
+// * * * * * * * * * * * * Protected Member Functions * * * * * * * * * * * //
+
+void Foam::functionObjects::energySpectrum::writeFileHeader(Ostream& os)
+{
+ writeHeader(os, "Turbulence energy spectra");
+
+ writeCommented(os, "kappa E(kappa)");
+
+ os << endl;
+}
+
+
+void Foam::functionObjects::energySpectrum::calcAndWriteSpectrum
+(
+ const vectorField& U,
+ const vectorField& C,
+ const vector& c0,
+ const vector& deltaC,
+ const Vector<label>& N,
+ const scalar kappaNorm
+)
+{
+ Log << "Computing FFT" << endl;
+ const complexVectorField Uf
+ (
+ fft::forwardTransform
+ (
+ ReComplexField(U),
+ List<label>({N.x(), N.y(), N.z()})
+ )
+ /scalar(cmptProduct(N))
+ );
+
+
+ Log << "Computing wave numbers" << endl;
+ const label nMax = cmptMax(N);
+ scalarField kappa(nMax);
+ forAll(kappa, kappai)
+ {
+ kappa[kappai] = kappai*kappaNorm;
+ }
+
+ Log << "Computing energy spectrum" << endl;
+ scalarField E(nMax, 0);
+ const scalarField Ec(0.5*magSqr(Uf));
+ forAll(C, celli)
+ {
+ point Cc(C[celli] - c0);
+ label i = round((Cc.x() - 0.5*deltaC.x())/(deltaC.x())*(N.x() - 1));
+ label j = round((Cc.y() - 0.5*deltaC.y())/(deltaC.y())*(N.y() - 1));
+ label k = round((Cc.z() - 0.5*deltaC.z())/(deltaC.z())*(N.z() - 1));
+ label kappai = round(Foam::sqrt(scalar(i*i + j*j + k*k)));
+
+ E[kappai] += Ec[celli];
+ }
+
+ E /= kappaNorm;
+
+ Log << "Writing spectrum" << endl;
+ autoPtr<OFstream> osPtr = createFile(name(), time_.value());
+ OFstream& os = osPtr.ref();
+ writeFileHeader(os);
+
+ forAll(kappa, kappai)
+ {
+ os << kappa[kappai] << tab << E[kappai] << nl;
+ }
+}
+
+
+// * * * * * * * * * * * * * * * * Constructors * * * * * * * * * * * * * * //
+
+Foam::functionObjects::energySpectrum::energySpectrum
+(
+ const word& name,
+ const Time& runTime,
+ const dictionary& dict
+)
+:
+ fvMeshFunctionObject(name, runTime, dict),
+ writeFile(mesh_, name),
+ cellAddr_(mesh_.nCells()),
+ UName_("U"),
+ N_(Zero),
+ c0_(Zero),
+ deltaC_(Zero),
+ kappaNorm_(0)
+{
+ read(dict);
+}
+
+
+// * * * * * * * * * * * * * * * Member Functions * * * * * * * * * * * * * //
+
+bool Foam::functionObjects::energySpectrum::read(const dictionary& dict)
+{
+ fvMeshFunctionObject::read(dict);
+ writeFile::read(dict);
+
+ dict.readIfPresent("U", UName_);
+
+ const boundBox meshBb(mesh_.bounds());
+
+ // Assume all cells are the same size...
+ const cell& c = mesh_.cells()[0];
+ boundBox cellBb(boundBox::invertedBox);
+ forAll(c, facei)
+ {
+ const face& f = mesh_.faces()[c[facei]];
+ cellBb.add(mesh_.points(), f);
+ }
+
+ const vector L(meshBb.max() - meshBb.min());
+ const vector nCellXYZ(cmptDivide(L, cellBb.max() - cellBb.min()));
+
+ N_ = Vector<label>
+ (
+ round(nCellXYZ.x()),
+ round(nCellXYZ.z()),
+ round(nCellXYZ.z())
+ );
+
+ // Check that the mesh is a structured box
+ vector cellDx(cellBb.max() - cellBb.min());
+ vector expectedMax(N_.x()*cellDx.x(), N_.y()*cellDx.y(), N_.z()*cellDx.z());
+ vector relativeSize(cmptDivide(L, expectedMax));
+ for (direction i = 0; i < 3; ++i)
+ {
+ if (mag(relativeSize[i] - 1) > 1e-3)
+ {
+ FatalErrorInFunction
+ << name() << " function object is only appropriate for "
+ << "isotropic structured IJK meshes. Mesh extents: " << L
+ << ", computed IJK mesh extents: " << expectedMax
+ << exit(FatalError);
+ }
+ }
+ Log << "Mesh extents (deltax,deltay,deltaz): " << L << endl;
+ Log << "Number of cells (Nx,Ny,Nz): " << N_ << endl;
+
+ // Map into i-j-k co-ordinates
+ const vectorField& C = mesh_.C();
+ c0_ = returnReduce(min(C), minOp<vector>());
+ const vector cMax = returnReduce(max(C), maxOp<vector>());
+ deltaC_ = cMax - c0_;
+
+ forAll(C, celli)
+ {
+ label i = round((C[celli].x() - c0_.x())/(deltaC_.x())*(N_.x() - 1));
+ label j = round((C[celli].y() - c0_.y())/(deltaC_.y())*(N_.y() - 1));
+ label k = round((C[celli].z() - c0_.z())/(deltaC_.z())*(N_.z() - 1));
+
+ cellAddr_[celli] = k + j*N_.y() + i*N_.y()*N_.z();
+ }
+
+ kappaNorm_ = constant::mathematical::twoPi/cmptMax(L);
+
+ return true;
+}
+
+
+bool Foam::functionObjects::energySpectrum::execute()
+{
+ return true;
+}
+
+
+bool Foam::functionObjects::energySpectrum::write()
+{
+ const auto& U = mesh_.lookupObject<volVectorField>(UName_);
+ const vectorField& Uc = U.primitiveField();
+ const vectorField& C = mesh_.C();
+
+ if (Pstream::parRun())
+ {
+ PstreamBuffers pBufs(Pstream::commsTypes::nonBlocking);
+
+ UOPstream toProc(0, pBufs);
+
+ toProc << Uc << C << cellAddr_;
+
+ pBufs.finishedSends();
+
+ if (Pstream::master())
+ {
+ const label nGlobalCells(cmptProduct(N_));
+ vectorField Uijk(nGlobalCells);
+ vectorField Cijk(nGlobalCells);
+
+ for (label proci = 0; proci < Pstream::nProcs(); ++proci)
+ {
+ UIPstream fromProc(proci, pBufs);
+ vectorField Up;
+ vectorField Cp;
+ labelList cellAddrp;
+ fromProc >> Up >> Cp >> cellAddrp;
+ UIndirectList<vector>(Uijk, cellAddrp) = Up;
+ UIndirectList<vector>(Cijk, cellAddrp) = Cp;
+ }
+
+ calcAndWriteSpectrum(Uijk, Cijk, c0_, deltaC_, N_, kappaNorm_);
+ }
+
+ }
+ else
+ {
+ vectorField Uijk(Uc, cellAddr_);
+ vectorField Cijk(C, cellAddr_);
+
+ calcAndWriteSpectrum(Uijk, Cijk, c0_, deltaC_, N_, kappaNorm_);
+ }
+
+ return true;
+}
+
+
+// ************************************************************************* //
diff --git a/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.H b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.H
new file mode 100644
index 0000000000000000000000000000000000000000..9958d6edbe7f412a74defc63adb2a9bcba0a8f7d
--- /dev/null
+++ b/src/functionObjects/randomProcesses/energySpectrum/energySpectrum.H
@@ -0,0 +1,178 @@
+/*---------------------------------------------------------------------------*\
+ ========= |
+ \\ / F ield | OpenFOAM: The Open Source CFD Toolbox
+ \\ / O peration |
+ \\ / A nd | Copyright (C) 2018 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::energySpectrum
+
+Group
+ grpFieldFunctionObjects
+
+Description
+ Calculates the energy spectrum for a structured IJK mesh
+
+Usage
+ Example of function object specification:
+ \verbatim
+ energySpectrum1
+ {
+ type energySpectrum;
+ libs ("libfieldFunctionObjects.so");
+ ...
+ log yes;
+ }
+ \endverbatim
+
+ Where the entries comprise:
+ \table
+ Property | Description | Required | Default value
+ type | type name: energySpectrum | yes |
+ log | write info to standard output | no | yes
+ \endtable
+
+ Output data is written to the file \<timeDir\>/energySpectrum.dat
+
+See also
+ Foam::functionObjects::fvMeshFunctionObject
+ Foam::functionObjects::writeFile
+
+SourceFiles
+ energySpectrum.C
+ energySpectrumTemplates.C
+
+\*---------------------------------------------------------------------------*/
+
+#ifndef functionObjects_energySpectrum_H
+#define functionObjects_energySpectrum_H
+
+#include "fvMeshFunctionObject.H"
+#include "writeFile.H"
+#include "Vector.H"
+#include "vectorField.H"
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+namespace Foam
+{
+namespace functionObjects
+{
+
+/*---------------------------------------------------------------------------*\
+ Class energySpectrum Declaration
+\*---------------------------------------------------------------------------*/
+
+class energySpectrum
+:
+ public fvMeshFunctionObject,
+ public writeFile
+{
+protected:
+
+ // Protected data
+
+ //- I-J-K mesh addressing
+ labelList cellAddr_;
+
+ //- Name of velocity field, default = U
+ word UName_;
+
+ //- Number of cells in I-J-K directions
+ Vector<label> N_;
+
+ //- Reference point
+ vector c0_;
+
+ //- Cell length scale
+ vector deltaC_;
+
+ //- Wave number
+ scalar kappaNorm_;
+
+
+ // Protected Member Functions
+
+
+ //- Output file header information
+ virtual void writeFileHeader(Ostream& os);
+
+ //- Calculate and write the spectrum
+ void calcAndWriteSpectrum
+ (
+ const vectorField& U,
+ const vectorField& C,
+ const vector& c0,
+ const vector& deltaC,
+ const Vector<label>& N,
+ const scalar kappaNorm
+ );
+
+ //- No copy construct
+ energySpectrum(const energySpectrum&) = delete;
+
+ //- No copy assignment
+ void operator=(const energySpectrum&) = delete;
+
+
+public:
+
+ //- Runtime type information
+ TypeName("energySpectrum");
+
+
+ // Constructors
+
+ //- Construct from Time and dictionary
+ energySpectrum
+ (
+ const word& name,
+ const Time& runTime,
+ const dictionary& dict
+ );
+
+
+ //- Destructor
+ virtual ~energySpectrum() = default;
+
+
+ // Member Functions
+
+ //- Read the field min/max data
+ virtual bool read(const dictionary&);
+
+ //- Execute, currently does nothing
+ virtual bool execute();
+
+ //- Write the energySpectrum
+ virtual bool write();
+};
+
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+} // End namespace functionObjects
+} // End namespace Foam
+
+// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
+
+#endif
+
+// ************************************************************************* //