foam-extend4.1-coherent-io/applications/solvers/solidMechanics/elasticThermalSolidFoam/createFields.H

    Info<< "Reading field U\n" << endl;
    volVectorField U
    (
        IOobject
        (
            "U",
            runTime.timeName(),
            mesh,
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE
        ),
        mesh
    );

    //     volTensorField gradU = fvc::grad(U);
    volTensorField gradU
    (
        IOobject
        (
	 "grad(U)",
	 runTime.timeName(),
	 mesh,
	 IOobject::NO_READ,
	 IOobject::NO_WRITE
	 ),
        mesh,
        dimensionedTensor("zero", dimless, tensor::zero)
     );
    //surfaceVectorField snGradU = fvc::snGrad(U);
    surfaceVectorField snGradU
    (
        IOobject
        (
            "snGrad(U)",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::NO_WRITE
        ),
        mesh,
	dimensionedVector("zero", dimless, vector::zero)
    );

    volSymmTensorField epsilon
    (
        IOobject
        (
            "epsilon",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimless, symmTensor::zero)
    );

    Info<< "Reading field T\n" << endl;
    volScalarField T
    (
        IOobject
        (
            "T",
            runTime.timeName(),
            mesh,
            IOobject::MUST_READ,
            IOobject::AUTO_WRITE
        ),
        mesh
    );

    volSymmTensorField sigma
    (
        IOobject
        (
            "sigma",
            runTime.timeName(),
            mesh,
            IOobject::READ_IF_PRESENT,
            IOobject::AUTO_WRITE
        ),
        mesh,
        dimensionedSymmTensor("zero", dimForce/dimArea, symmTensor::zero)
    );

    volVectorField divSigmaExp
    (
        IOobject
        (
            "divSigmaExp",
            runTime.timeName(),
            mesh,
            IOobject::NO_READ,
            IOobject::NO_WRITE
        ),
        mesh,
        dimensionedVector("zero", dimensionSet(1,-2,-2,0,0,0,0), vector::zero)
    );

    surfaceVectorField n = mesh.Sf()/mesh.magSf();

    // mechanical properties
    constitutiveModel rheology(sigma, U);

    volScalarField rho = rheology.rho();

    volScalarField mu = rheology.mu();
    volScalarField lambda = rheology.lambda();
    surfaceScalarField muf = fvc::interpolate(mu, "mu");
    surfaceScalarField lambdaf = fvc::interpolate(lambda, "lambda");


    // thermal properties
    Info<< "Reading thermal model\n" << endl;
    thermalModel thermal(T);

    volScalarField C = thermal.C();
    volScalarField k = thermal.k();
    volScalarField threeKalpha = rheology.threeK()*rho*thermal.alpha();
    surfaceScalarField threeKalphaf = fvc::interpolate(threeKalpha, "threeKalpha");
    volScalarField T0 = thermal.T0();
    volScalarField rhoC = rho*C;


// for aitken relaxation
volVectorField aitkenDelta
   (
        IOobject
        (
	 "aitkenDelta",
	 runTime.timeName(),
	 mesh,
	 IOobject::NO_READ,
	 IOobject::NO_WRITE
	 ),
        mesh,
        dimensionedVector("zero", dimLength, vector::zero)
    );
// aitken relaxation factor
scalar aitkenInitialRes = 1.0;
scalar aitkenTheta = 0.01;
// if(mesh.relax(U.name()))
//   {
//     aitkenTheta = mesh.relaxationFactor(U.name());
//   }