Erguns equ as a source term
 

Hi,

I have a single phase of a liquid flow and I want to calculate the pressure drop based on Erguns equation in fluent as a source term and I am wondering how I should define S and dS. Since the Ergun is
(A+B*U)*U
then I assume it should be
S=(A+B*magU)*U
and I am wondering if dS should be as
dS=A+B*magU
but then as I know dS is the decay part for the linearized equation and shold be negative, correct?