[Roscoe341]

Hi. I am trying to simulate the flow of air though a packed rock bed in ANSYS Fluent. The flow resistance in the bed is anisotropic. As far as i understand the best way to simulate an anisotrpic porous media is by adding a momentum source term to the standard fluid flow equations. I have the resistance tensor but am not sure how to implement it in Ansys with a UDF. My resistance tensor is below.

𝑆𝑥 = 𝜇𝑢𝑥𝐷𝑥𝑥 + 𝜇𝑢𝑦𝐷𝑥𝑦 + 𝜇𝑢𝑧𝐷𝑥𝑧 + 1 2 𝜌|𝑢|{𝑢𝑥𝐶𝑥𝑥 + 𝑢𝑦𝐶𝑥𝑦 + 𝑢𝑧𝐶𝑥𝑧}

𝑆𝑦 = 𝜇𝑢𝑥𝐷𝑦𝑥 + 𝜇𝑢𝑦𝐷𝑦𝑦 + 𝜇𝑢𝑧𝐷𝑦𝑧 + 1 2 𝜌|𝑢|{𝑢𝑥𝐶𝑥𝑦 + 𝑢𝑦𝐶𝑦𝑦 + 𝑢𝑧𝐶𝑦𝑧}

𝑆𝑧 = 𝜇𝑢𝑥𝐷𝑧𝑥 + 𝜇𝑢𝑦𝐷𝑧𝑦 + 𝜇𝑢𝑧𝐷𝑧𝑧 + 1 2 𝜌|𝑢|{𝑢𝑥𝐶𝑧𝑥 + 𝑢𝑦𝐶𝑧𝑦 + 𝑢𝑧𝐶𝑧𝑧 }

I also have the values for the D and C matrix.

Any assistance in setting up this problem would be much appreciated.

Thanks

[AlexanderZ]

you may try to use this link to make your code
UDF - Anisotropic Conductivity

to make define momentum source you need define_source macro, not DEFINE_ANISOTROPIC_CONDUCTIVITY