output value vs paraFoam?

[kimy]

I am checking that the variables outbut from source code in solver and I found the differences between output and paraFoam. I cannot understand why it happened? The follow is my codes in simpleFoam.C:
**const dimensionedScalar myZero("myZero", dimensionSet(0,0,0,0,0,0,0),scalar(0) );

volScalarField k0=myZeroturbulence->k();
volScalarField nut0=myZeroturbulence->nut();
volScalarField nu0=myZero*turbulence->nu();

const label patchID = mesh.boundaryMesh().findPatchID("wall");
const tmp<scalarField> tnuw = turbulence->nu(patchID);
const scalarField& nuw = tnuw();

const tmp<scalarField> tnutw = turbulence->nut(patchID);
const scalarField& nutw = tnutw();

const fvPatchVectorField& Uw = turbulence->U().boundaryField()[patchID];

const scalarField magGradUw(mag(Uw.snGrad()));

for (int j=0; j<nut0.size(); j++)
{
if (j<=(nutw.size()/2-1)) {nut0[j]=nutw[j]; nu0[j]=nuw[j];}
if (j>=(mesh.cells().size()-nutw.size()/2)&&j<=mesh.cells().size()-1) {nut0[j]=nutw[j-(mesh.cells().size()-nutw.size())];nu0[j]=nuw[j-(mesh.cells().size()-nutw.size())];}
}

volVectorField Uww=U*myZero;
const fvPatchList& patches = mesh.boundary();
labelList wallList;
wallList.clear();

forAll(patches, patchi)
{
const fvPatch& curPatch = patches[patchi];
if (isType<wallFvPatch>(curPatch))
{
forAll(curPatch, facei)
{
label faceCelli = curPatch.faceCells()[facei];
wallList.resize(wallList.size()+1);
wallList[wallList.size()-1]=faceCelli;
}
}
}

forAll(wallList,i)
{

Uww[wallList[i]] = U[wallList[i]];

}

volScalarField uz = Uww.component(vector::Z);
volVectorField SG = uz*vector(0,0,1);
volScalarField magGradUww=mag(SG)/myY;

k0=((nut0+nu0)*magGradUww/0.3);

Info<<"k0="<<k0<<endl;
Info<<"nut0="<<nut0<<endl;
Info<<"nutw="<<nutw<<endl;
Info<<"magGradUww="<<magGradUww<<endl;
Info<<"magGradUw="<<magGradUw<<endl;
Info<<"tauw="<<(nut0+nu0)magGradUww<<endl;
Info<<"Uw="<<Uw<<endl;*

nutw and magGradUw are copied from nutkwallfunction. In the end, wallshearstress in the paraFoam is not the same as (nut0+nu0)*magGradUww.