Multicomponent SC method

Dear all,
I developed a Multicomponent LB code (D2Q9) based on the SC method as described in Sukop’s book. I have two question about calculating the velocity and pressure of the bulk flow:

  1. In this book, the interaction potential function (psi) of each component is equal to the density (rho). Is this the best function for Multicomponent SC model? If not, can anyone help me to find the most suitable function for psi?
  2. In the book, the composite (or common) velocity u’ is presented as the velocity of the bulk flow. But in some references I find the sum of (rho,ku,k+1/2F,k) as velocity of bulk flow (k is the k’th component). Which is really correct?
  3. How I can calculate the pressure of each component? I know that I should add a term to the single component pressure (1/3*rho), but I am not confident of the correct additional term.

Many Thanks.