I am I trying to solve for the following UDS flux function using the DEFINE_UDS_FLUX macro:

alpha del.(UDS0) or alpha nabla(UDS0)

I got this UDF (simplified) back from the fluent guys:

F_AREA(A, f, thread);

duds0dx = C_UDSI_G(c0, tc0, 0)[0];

dudsi0dy = C_UDSI_G(c0, tc0, 0)[1];

return alpha * (duds0dx*A[0] + duds0dy*A[1]);

My question is this: Do I need the face areas A[0] and A[1] in my return function? They are playing havoc with my results and making thre returned function look rather unphysical. Any comments would be greatly appreciated.

Hi Andrew, I think these expressions are correct if you have to define the term del(alpha del[UDS0]) as in your old message, in this way you convert a volumetric term in a flux. About the face areas: ...you have to watch if they are positive or negative, maybe this changes your resuls???Let me know... and please, if you can, give a look to my last message http://www.cfd-online.com/Forum/fluent.cgi?read=24397 .

Giordano Bruno