This is a good question, since I haven’t seen anywhere clear description of porous media setup in OpenFOAM.
Quickly answering your questions based on my modest experience:
First of all, if you want to create non-isotropic porous media, you should put the value of ‘f’ and ‘d’ coeffs only in those directions you interested in. So if you media flows in X direction, put values only in ‘x value’ field. Zeroes in other fields will mean that in Darcy-Forchheimer equation drag is being created only on x direction:
The second thing: e1, e2 are the principal directions, so your porous media will be aligned along this directions. For example, if you have a porous zone inclined of 45° with respect to the x direction of the reference frame in your mesh, you should replace e1 with something like (in 2D)
e1 (0.70710678 0.70710678 0)
If you keep
e2 (0 0 1)
the second direction is parallel to the z axis.
For example, in my case I set up e1 and e2 vectors the way you can see at the pic:
And you can look at this project as a reference as well: link
And the last thing I should mention is the exact values of ‘d’ and ‘f’ coefficients calculation. Unfortunately, I didn’t calculate them for my case myself, but used help of colleague of mine. I’m not sure how he did it, but I know that he used reference book with experimental values of porosity for our media and dimensions of ‘d’ and ‘f’ coeffs , after he gave me numbers we made a simple simulation in tube to prove those numbers work fine. I’ll try to reach my colleague and find out more details.
Hope this will give you right direction to move!