[BlackHeartInertia]

Hello everyone,

I'm a student and I'm new in this of the CFD.
I was reading about cfd and I was wondering if can someone say me the difference between a 3x3 matrix and a tensor? I can't get it.
I'm learning this by my own because is for the university and we never see tensors at class... so as it is related to turbulence models I'm a little confused.

Bye

[FMDenaro]

Originally Posted by BlackHeartInertia

Hello everyone,

I'm a student and I'm new in this of the CFD.
I was reading about cfd and I was wondering if can someone say me the difference between a 3x3 matrix and a tensor? I can't get it.
I'm learning this by my own because is for the university and we never see tensors at class... so as it is related to turbulence models I'm a little confused.

Bye

Well, a second order tensor is actually expressed as a matrix. For example, the tensor (vv) can be expressed in a 3x3 matrix (3D) or 2x2 matrix (2D). I suggest to study the issue in a good textbook.

[agd]

A matrix is simply an array of numbers. A second rank tensor can be represented by a matrix in a fashion similar to how a vector (a rank 1 tensor) can be represented by an nx1 matrix (a column vector). The form that helped me understand tensors best is the dyad representation. If you are familiar with basic vector algebra, then pursuing this form may help make things clearer.

[BlackHeartInertia]

Thank you very much

[BlackHeartInertia]

If anyone read this, I make a post but I have an aditional question.
It is that I would like to know when the demoninator in the e equation vanishes or becomes smaller than zero, and why the standard k-e uses wall functions.
Are this things related?

The realizable k-e changes the demonnator "k" by "k+sqrt(nu*epsilon])" in the e equation


Thanks

[terry9o]

I am also confused about that.