Mixing 2 Fluids in an External Analysis

Hi Everyone,

I have an example where I have propane moving through a hose/tube to a point where it will be released to air. I have attached an image to help explain this.

My question is, how would I set this up as an EXTERNAL analysis? I know fluid mixing is fairly easy with INTERNAL analysis, but can't find any examples where it has been done using EXTERNAL.

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