Hello! Sir! Finally, I got the right results of mass flux of a species, but I do not know why the velocity vector is changed? When we add mass source, does it mean that we add velocity as well? You can see the results of my velocity vector before adding mass source and after adding mass source.n1/ Velocity vector before adding mass sourcen2/ Velocity vector after adding mass source of a speciesnI really thank you for spending your precious time to help me so far, I hope you will keep replying to my question. Thanks!nn