I have researched online and cannot seem to find any resources to this affect. I am running SW flow 2018 SP5. Any help would be appreciated.
Long time no see. The external flow setup you are looking for is a near default external flow setup. I'd suggest having gravity on especially if you happen to take your exhaust tube off vertical.
Make sure you have both your fluids selected for this project:
Then make sure the default ambient flow condition is air only so it starts as an air-only computational domain.
Then your only flow boundary condition would be an inlet flow of 100% methane:
The result is a mixed gas plume:
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