Thanks for your response — but I think there might be a misunderstanding about what I'm trying to do.

My post wasn’t referring to the lid-driven cavity case at all. That’s a classic benchmark problem with a moving wall driving recirculation in a closed cavity. In contrast, I’m dealing with external wind flow around a building and how it affects indoor airflow — which is a completely different setup, involving open boundaries and fluid entering and exiting the building.

What I’m exploring is a one-way coupling approach, where:

I fully understand that air is a single continuum medium — but in practice, many researchers and engineers split the domain for efficiency and treat the interface using mapped boundary conditions. This is especially useful when the external conditions don’t change much between internal cases, and full-domain simulations would be too costly.

The term "coupling" here refers to transferring data between simulations, not necessarily solving both domains simultaneously or in a two-way fashion. Fluent and other tools (e.g., OpenFOAM) support this kind of patched boundary condition workflow.

I do agree that if the external and internal flows are highly interactive, then a fully coupled model would be ideal — and I mentioned in my post that I plan to run at least one expensive full-domain simulation to compare with the simplified model and validate the approach.

If anyone has experience with using this method in Fluent (e.g., using Patch, Profile, or Interpolation features), I’d really appreciate practical advice or references.

I'm not sure why your confusing with temperature, I'm doing ventilation analysis.