[Fan.zx]

I'm running a bubble column reactor simulation with Eulerian Multiphase model.

Primary phase is water. The second phase is air and dispersed.
As a transient simulation, the solution is converged to a steady state now.
I'm trying to inject a tracer to calculate the axial dispersion coefficient. I searched for all kinds of methods, such as inlet diffusion (single phase only) , patch, cell zone source, add a third phase(with the same properties as water, doesn't make physical sense). None of them seems to work.
Could somebody be kind enough to give me some step by step tips on how to simulate the injection of a tracer?