upwinding in the convective term

Steve Moore

Hi

In the convective term of the discretized momentum equation you have the sum over all the faces of rho_f*u_f*phi_f . A_f and when upwinding is discussed they say that the face value of phi_f is set equal to the value at the centre of the upstream cell (for a first order upwinding scheme that is). I have two questions regarding this. First of all, phi_f IS u_f, so you don't know it in advance. So when the matrix equation

a_p phi_p = sum a_n phi_n + b

is formed

u_f is in the a_p and a_n coefficients... so you need the value for the thing you're trying to solve for! Does fluent get around this by using the value for u_f from the previous iteration? Secondly is the value of u_f upwinded the same as phi_f?

Steve