Hi Balakaya612,
So, the error is based on using two Output Objects.
My suggestion would be to write OpenVDB files out and use materials as you need those. This is a wild guess, because:
I struggle to see how that is even remotely working in a believable visual way (not to talk about physics by now), as the different scatter results must be based on differences in the sources. How those sources and their obviously and requested different results (e.g., Scatter) would not interfere with each other in such a dynamic scenario is beyond me. But with separate setups, that is not a give; perhaps introducing Particles into the mix might help. My theoretical (or call it a wild guess) conclusion is that it will not work if I just use two independent sources.
Perhaps the best way to explain it would be to use the dynamics and complexity of weather prediction, which is also based on air movements. Which is so complex that we struggle to make long-term predictions.
Now, with sources, the turbulences and the complexity are limited but interactive. It does not influence the other; that influence affects an infinite loop. How much that can be recognized is unclear to me, as it is a question of perception and the level of detailed observation, but it surely is not a single bilateral effect.
Perhaps you have some reference photos that show how that works so I can explore it.
Cheers