[darlopez]

Hi everybody.
I have a dynamic mesh and I want to keep the orthogonality between cells. I use a directional diffusivity, it seems like:

diffusivity directional ( a b c );

in my dynamicMeshDict archive.

a,b and c are numbers, can anybody tell me what mean these numbers?

I found two versions. One of them says that this numbers are the value of the coefficient of diffusion in the 3 directions of the space. The other says that the first number determines the mean cell non-orthogonality, while the second number determines the mean cell skewness (and the third?). But in my experience I can not determine this numbers correctly.
How can I determine the value of a,b and c?

What other types of diffusivity I can use to keep the orthogonality between cells?

Thanks a lot.