Butterfly outdoor wind simulation with surrounding building-gradding issue

Hi, I am working on outdoor wind simulation for my project. I want to focus on target building and the surrouding buildings could be considered as obstacles during simulation. However, I don’t know how to write the definition. Then I tried another way, to add all buildings in the BFgeometry with big cell size, then to refine the mesh abound target building, i.e. to have narrower grid arroung the target building(highlighted in the picture), anyone knows how to do it?

outdoor_airflow-1.gh (730.5 KB)
Rhino file:https://drive.google.com/file/d/1Z5zgi8LkoXBKG8ooHmgqtvXCA7eVTJkv/view?usp=sharing