Hello

I have a problem! First I coded LBM based on shan-chen method that is described on sukop’s book then because i want to simulate porous media i changed my collision operator(BGK) to Multi Relaxation Time(MRT). My problem is when i added interaction forces to distribution function after collision step by formula 3*wt*(ex*gr_x + ey*gr_y) in which gr_x and gr_y are interaction forces in X and Y direction, my results are very good in Poiseuille Flow by any matrix of relaxation time that the parameters have a value of 0.5-2.0 (s0,s3 and s5 =0 in Relaxation Matrix(s0 s1 s2 s3 s4 s5 s6 s7 s8 s9)) but when i want to simulate Contact angle of droplet in surface my results are not very good for some of the variables of G (adhesion coefficient) .But when I added interaction forces by shifting the velocity the results are acceptable. I guess when i add interaction forces to distribution function maybe the formula 3*wt*(ex*gr_x + ey*gr_y) is not comprehensive can not be used in this case or maybe some other changes should be made. Your help is appreciated.

Amir.