[NazarioM]

Hello FOAMers,
I am new to OpenFOAM and not very experienced with C++ so my questions might be very trivial for many/most of you. However, I have not been able to find an exhaustive answer, so...
I need to compute the eigenvectors of a volTensorField E. eigenVectors(E) returns a volTensorField, but how can I get each individual eigenvector? From what I have read, they should be defined in the internalField, as lines, but I haven't been able to get them.
From what I understand, there is no direct way of extracting a vector from a tensor, so I thought I could compute the eigenvalues first and then the corresponding eigenvector for each eigenvalue. However, I'm facing the same issue when I use eigenValues(E) (a volVectorField): for some reason, I am not able to extract each individual eigenvalue.
Can anyone explain to me how to do?

Thanks in advance,
N.

[HPE]

You can access a tensor within volTensorField by using square brackets, e.g.

const auto eVecs = eigenVectors(E);
const auto eVec = eVecs[0]; // first element within the list.

Hope didnt misunderstand your question.

[NazarioM]

Originally Posted by HPE

You can access a tensor within volTensorField by using square brackets, e.g.

const auto eVecs = eigenVectors(E);
const auto eVec = eVecs[0]; // first element within the list.

Hope didnt misunderstand your question.

Thank you for your answer, HPE. Unfortunately, it did not work, as I get an error saying "no match for operator []".
I have come up with a workaround, calculating the eigenvalues first and then the corresponding eigenvector for each eigenvalue. However I can only obtain the values in the internalField in this way (because I use forAll cellI). I would need my eigenvectors to be defined over the entire domain, boundary included.
Do you have any other solution?

[NazarioM]

Update:

It is sufficient to multiply eigenVectors(T) by a vector vx(1,0,0) to extract the first eigenvector (first row of eigenVectors(T)), and similarly for the other two.

[HPE]

Could you please share a bit of code, otherwise difficult to follow what needs to be done?