Creating a case form geometries is used for indoor simulations. Your geometry defines the computational domain.
Creating a case from tunnel is used for outdoor wind tunnel simulations. A virtual wind tunnel defines the computational domain that includes your geometry.
Thanks for your response.
Could creating a case from tunnel be used for (indoor+outdoor) simulations for geometry with window?
@WuMinShiun The answer is yeah.I have done indoor+outdoor CFD simulation in similar project.