[Charlieman95]

Hello.
Do anybody know or have any idea of how To get or compute the X_component of the skin coefficient in SU2.
The case is a turbulent flow over an airfoil.
Thanks.

[fpalacios]

Hi Carlos, that is an important capability that we should implement in SU2.

At this point, if you need that result my recommendation is to go to

void CNSSolver::Viscous_Forces(CGeometry *geometry, CConfig *config) {

in solver_direct_mean()
and change

/*--- Project Tau in each surface element ---*/

for (iDim = 0; iDim < nDim; iDim++) {
TauElem[iDim] = 0.0;
for (jDim = 0; jDim < nDim; jDim++) {
TauElem[iDim] += Tau[iDim][jDim]*UnitNormal[jDim];
}
}

/*--- Compute wall shear stress (using the stress tensor) ---*/

TauNormal = 0.0; for (iDim = 0; iDim < nDim; iDim++) TauNormal += TauElem[iDim] * UnitNormal[iDim];
for (iDim = 0; iDim < nDim; iDim++) TauTangent[iDim] = TauElem[iDim] - TauNormal * UnitNormal[iDim];
WallShearStress = 0.0; for (iDim = 0; iDim < nDim; iDim++) WallShearStress += TauTangent[iDim]*TauTangent[iDim];
WallShearStress = sqrt(WallShearStress);

for (iDim = 0; iDim < nDim; iDim++) WallDist[iDim] = (Coord[iDim] - Coord_Normal[iDim]);
WallDistMod = 0.0; for (iDim = 0; iDim < nDim; iDim++) WallDistMod += WallDist[iDim]*WallDist[iDim]; WallDistMod = sqrt(WallDistMod);

/*--- Compute wall skin friction coefficient, and heat flux on the wall ---*/

CSkinFriction[iMarker][iVertex] = WallShearStress / (0.5*RefDensity*RefVel2);


by

/*--- Project Tau in each surface element ---*/

for (iDim = 0; iDim < nDim; iDim++) {
TauElem[iDim] = 0.0;
for (jDim = 0; jDim < nDim; jDim++) {
TauElem[iDim] += Tau[iDim][jDim]*UnitNormal[jDim];
}
}

/*--- Compute wall shear stress (using the stress tensor) ---*/

TauNormal = 0.0; for (iDim = 0; iDim < nDim; iDim++) TauNormal += TauElem[iDim] * UnitNormal[iDim];
for (iDim = 0; iDim < nDim; iDim++) TauTangent[iDim] = TauElem[iDim] - TauNormal * UnitNormal[iDim];
WallShearStress = 0.0; for (iDim = 0; iDim < nDim; iDim++) WallShearStress += TauTangent[iDim]*TauTangent[iDim];
WallShearStress = sqrt(WallShearStress);

for (iDim = 0; iDim < nDim; iDim++) WallDist[iDim] = (Coord[iDim] - Coord_Normal[iDim]);
WallDistMod = 0.0; for (iDim = 0; iDim < nDim; iDim++) WallDistMod += WallDist[iDim]*WallDist[iDim]; WallDistMod = sqrt(WallDistMod);

/*--- Compute wall skin friction coefficient, and heat flux on the wall ---*/

TauTangent_X = TauElem[0] - TauNormal * UnitNormal[0];
CSkinFriction[iMarker][iVertex] = TauTangent_X / (0.5*RefDensity*RefVel2);

it is a very temporary ad hoc change but it will solve your problem... CSkinFriction[iMarker][iVertex] will have now the X Cf component.

Best,
Francisco