How to compute coefficients in Fluent???urgent!

Asghari

Hi all;

We know that for any scalar variable solution, there is a discretized form as: aP*Phi_p=aN*Phi_N+aS*Phi_S+aW*Phi_W+aE*Phi_E+b

My questions:

a)Is b physical source term ?

b)How to compute the coefficients(aP,aN,aS,aW,aE) in Fluent, specially for energy equation(phi=Temperature) and first order upwind method for discretization of convection term ?Is there a paper or example for this object?I studied a reference that gives this expression for instance for aP: aP=aN+aW+aS+aE+Fe-Fw+Fn-Fs-Sp(Fe , Fw , Fn , Fs are face mass flux for east ,west,north and south faces) whereas user's guide presents this relation: aP=aP=aN+aW+aS+aE-Sp.

Why is there these discrepancies ?

Thanks in advance for everybody answer my questions.