Humpback whales inspire better helicopter rotor blades
By Ben Coxworth
February 3, 2012
Oh, those humpback whales and their weird fins. First, they inspired more efficient wind turbines. Next, their unique qualities were copied by undersea turbines used to harness tidal flow energy. Now, they've led to rotor blades that allow helicopters to be more maneuverable. It all comes down to bumps along their leading edge, known as tubercles.
For animals that are so huge and heavy, humpback whales are surprisingly fast and agile underwater. This is because of the tubercles on the front of their pectoral fins. The protrusions cause the water to flow over the fins in such a way that extra lift is created. Applied to both wind and undersea turbines, such bumps give them more lift, too.
Rotor blades, on the other hand, are not so perfectly designed. When a helicopter is flying forward, the blade that is advancing forward (in the same direction as the aircraft) is traveling faster than the blade opposite it, which is retreating backward. This can cause the retreating blade to temporarily lose lift and experience a "dynamic stall." This in turn results in turbulence, places stress on the rotors and their control rods, and limits the top speeds and maneuverability of the helicopter.
If the retreating blade were able to generate more lift, however, the point at which it stalled would be delayed. That's where the tubercles come in.
Scientists from the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR) glued a series of six-millimeter-wide rubber bumps onto the edges of all four of a helicopter's rotor blades - 186 on each blade. The bumps have been patented as Leading-Edge Vortex Generators (LEVoGs).
After showing promising results in wind tunnel tests, the helicopter was tried out in actual flights by test pilots. Apparently, they noticed a definite improvement in performance. On subsequent flights, instruments will be present to actually measure the differences.
The researchers are now hoping that existing rotors could be inexpensively retrofitted with the LEVoGs, while new titanium blades could be made with them already milled into the metal.