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