leading-edge vortex

controlled separated flow

Controlled separation on a slender delta.

An airflow that lies midway between a steady streamline (laminar) flow and an unsteady (turbulent) flow. The flow separates at sharp leading edges as a result of the boundary-layer effect but does not break down into a turbulent airflow. Instead strong vortices are formed, which generate lift. This kind of flow is prevalent in delta and swept wing plan forms, particularly at high angles of attack. Also known as a leading-edge vortex.

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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.

High-tech 'shark skin' fails to boost speed

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.

Swift lift: birds may get a rise out of swirling air

"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.

Against all odds: how bugs take wing

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.