[alimea]

Hi guys
I defined the stress tensor as a volScalarField in createFields.H. Then I calculated it as:

volTensorField gradU = fvc::grad(U);
tauS = etaS*twoSymm(gradU);

Then I converted stress tensor components to Cylindrical Coordinates using cylindricalCoordinates.H:

const volVectorField C = mesh.C(); // Initial Coordinates
const volVectorField CT = C-origin_; // Transfomed Coordinates

forAll(C,i)
{
 scalar teta = std::atan2(CT[i].y(), CT[i].x()); 
 if (teta < 0)
 {
     teta += 2*PI;  
 }
 scalar sin = Foam::sin(teta);
 scalar cos = Foam::cos(teta);
 
 // velocity field
 UC[i].x() =  U[i].x()*cos + U[i].y()*sin; // R component
 UC[i].y() = -U[i].x()*sin + U[i].y()*cos; // theta component
 UC[i].z() =  U[i].z();    // Z component
 
 // Solvent Stress Tensor
 tauSRT[i].xx() = tauS[i].xx()*pow(cos,2) + tauS[i].yy()*pow(sin,2) + 2 * tauS[i].xy()*cos*sin;    // TauS_rr
 tauSRT[i].xy() = ( tauS[i].yy() - tauS[i].xx() )*cos*sin + tauS[i].xy() * ( pow(cos,2) - pow(sin,2) );  // TauS_rt
 tauSRT[i].xz() = tauS[i].xz()*cos + tauS[i].yz()*sin;        // TauS_rz
 tauSRT[i].yy() = tauS[i].xx()*pow(sin,2) + tauS[i].yy()*pow(cos,2) - 2 * tauS[i].xy()*cos*sin;    // TauS_tt
 tauSRT[i].yz() = -tauS[i].xz()*sin + tauS[i].yz()*cos;        // TauS_tz
 tauSRT[i].zz() = tauS[i].zz();              // TauS_zz
}

and included it at the end of the runTime loop of the solver code, where all of the variables are calculated:

#include "cylindricalCoordinates.H"

We expected to see equal values for the magnitude of the stress tensor in XY and RT (R-teta), as I can see the same values for velocity in both coordinates system. However, the magnitude of the stress tensor in XY and RT are different! as you can see in the following picture:


Do you know what the problem is?