[wales]

Hello everyone,

I have a thesis related to heat transfer in radiators. Im newly experiencing fluent and have faced some unclear matters.
Firstly, I have to define a source term I have given in my attachment. But as you can see it has a partial differantial term(last term). So how can I write it via udf? Or an alternative to write this equation ?

Secondly, in my second attachment you see the diffusivity matrix. I guess the xx,yy,zz are indicators of the directions of x,y,z ? If so, what do the indicators
xy,yz,yx,zx etc. represent? Can anyone make this more clear?

Thank you.