Hi, I'm a student and new to CFX. I'm trying to model a simple paralle jet (injecting CH4) in a fully turbulent moving stream of air. I'm using the "k-epsilon" model combined with the "homogeneous multiphase flow model (interphase transfer model= none)". The velocityprofile downstream looks nicely bell-shaped as it should, but the concentration-profile does'nt seem to develop, as if only molecular diffusion takes place. The expansion of the half-radius of the concentration downstream, is way below the expansion of the half-radius of the velocity-profile downstream ...

Is it wrong to use the homogeneous model? What model should I use instead?

Sincerely - Peter N. S.

Sounds to me as though your solution hasn't had time to converge fully (although I could well be wrong). Are you running steady or transient? How many time steps did you give it. Make sure your convergence target is nice and low Res < 1e-5. You also might want to loosen the under-relaxation on your species.

If you have CH4 and air, then this is a multicomponent simulation, not a multiphase simulation. Multiphase means that the 'fluids' (which might be fluids or solids) do not mix at the molecular level...