What is the minimum distance between two objects until Falcon determines the gap is a solid object? I saw the example videos that showed models as large as a building and as small as a car. If the scale does not matter, if I put two rectangular towers next to each other how close can I put them until the air flow stops flowing between them?
This depends more on the resolution than the absolute dimensions of the geometry.
With lower resolution, the individual mesh elements will be large relative to passageways. At a certain point, they will consider a narrow gap to be essentially closed.
With higher resolution, relatively small gaps can be captured by the mesh and flow will move through.
You can view the plane as a grid or array of points to get a sense of the mesh resolution (note this visualization option isn't yet available in the Revit plugin)