This past summer I was watching my bees fanning and got told to move aside.
Sitting beside the entrance, which was about two feet from the ground, I
sighted along a line almost parallel to the the lower front corner of the
lowest hive body which constitutes the upper part of the entry.  The bees
were fanning as usual, and as usual there was a small "moustache" of bees
above the fanners along and above this upper corner.  They were chaining
themselves together, and the profile of their mass looked suspiciously like
one end of a venturi.  As the breeze shifted they would reposition
themselves.  Has anyone else noticed this?  Has anyone seen whether there is
a matching formation on the inside?  Are the "moustache" bees passively
aiding the fanners, perhaps reducing turbulence near the corner?