The denticles enhance this leading-edge vortex
. So my hypothesis is that these structures that make up shark skin reduce drag, but I also believe them to be thrust-enhancing," he said.
After all, notes Anders Henderstr6m of the University of Lund in Sweden, aeronautical engineers have long known that a swept-back wing with a sharp edge--the very shape of wings of fast-flying swifts--creates a leading-edge vortex
. Aircraft designers have used that wing architecture to create extra lift in some fighter jets and the now-retired supersonic transport the Concorde.
"As expected, we saw the leading-edge vortex
," Ellington said, "but as the smoke flowed around the vortex, we saw it suddenly make a right-angle turn and flow out strongly toward the wing tip." The moths, however, were still too small to see exactly when the vortex was being created.
This leading-edge vortex
lowers the air pressure over the upper surface of the maple seed, effectively sucking the wing upward to oppose gravity, giving it a boost.