Question

Non-orthogonality leads to ________ in diffusion problems.

(a) cubic-diffusion

(b) less-diffusion

(c) additional-diffusion

(d) cross-diffusion

I had been asked this question in unit test.

Question is from Diffusion Problem topic in section Diffusion Problem of Computational Fluid Dynamics

Answer 1

Correct option is (d) cross-diffusion

To explain I would say: In general, the surface vector of the non-orthogonal grids is given as the sum of the vector connecting the owner and the neighbour elements and an additional vector. This leads to an extra term in the diffusion equation called the cross-diffusion or non-orthogonal diffusion.