"Jay Honeck" wrote in message
ps.com...
Two vanes? What if they're pointed at each other?

Actually, even though they're three stories up, and separated by only
30 feet, I've already seen them briefly point at each other.

Wind swirling around building does some strange things. That is why they build
scale models of cities and put them in a wind tunnel, with a new proposed
skyscraper, to study the reactions.
--
Jim in NC