//- how explicit component of sigma is to be calculated
word divDSigmaExpMethod(mesh.solutionDict().subDict("stressedFoam").lookup("divDSigmaExp"));
Info << divDSigmaExpMethod << " method chosen for calculation of sigmaExp" << endl;
if
(
    divDSigmaExpMethod != "standard"
  && divDSigmaExpMethod != "surface"
  && divDSigmaExpMethod != "decompose"
  && divDSigmaExpMethod != "laplacian"
)
{
    FatalError << "divDSigmaExp method " << divDSigmaExpMethod << " not found!" << nl
        << "valid methods are:\nstandard\nsurface\ndecompose\nlaplacian"
        << exit(FatalError);
}