Aircraft

Humpback whales inspire better helicopter rotor blades

Humpback whales inspire better...
Kai Richter (left) and Holger Mai of DLR inspect the installation of humpback whale-inspired "LEVoGs" on the test helicopter
Kai Richter (left) and Holger Mai of DLR inspect the installation of humpback whale-inspired "LEVoGs" on the test helicopter
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The LEVoG-equipped DLR Bo 105 research helicopter
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The LEVoG-equipped DLR Bo 105 research helicopter
A humpback whale, with its tubercle-bearing pectoral fins
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A humpback whale, with its tubercle-bearing pectoral fins
Kai Richter with a single LEVoG
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Kai Richter with a single LEVoG
Kai Richter (left) and Holger Mai of DLR inspect the installation of humpback whale-inspired "LEVoGs" on the test helicopter
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Kai Richter (left) and Holger Mai of DLR inspect the installation of humpback whale-inspired "LEVoGs" on the test helicopter

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.

Kai Richter with a single LEVoG
Kai Richter with a single LEVoG

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.

Source: DLR via New Scientist

8 comments
christopher
You can only patent inventions, not discoveries. Sad that the patent examiner seems to have forgotten to tell these guys about that...
Anthony Parkerwood
These bumps just add a second dimension to the venturi, this should work on fixed wings aswell. Maybe even better if the entire top surface was covered in bumps. They should put a feathered edge on the back to see what effect it has.
see3d
@christopher: A patent is for a practical application of a discovery. A patent spells out how to duplicate the art. So a Patent for this could say that a bump of x dimensions spaced y apart on the leading edge of a helicopter rotor will improve performance. This is patentable if nobody did this before as normal practice. It is the patent examiner\'s job to make sure it is patentable and that only the parts that are truly unique are claimed.
Fretting Freddy the Ferret pressing the Fret
I want to see this implemented on computer fans. It would create less noise at the same number of rotations per second compared to the conventional fan design.
Gary Lanthrum
Vortex generators have been used on fixed wing aircraft for years, especially short takeoff and landing aircraft. A bush plane in Alaska without VG\'s is less common than one with them.
Mike Kling
Sorry Freddy, but I don\'t think this would affect fan blades. I think it only works on wings, or wing-like structures. And even then only on larger items. I haven\'t heard of any body trying vortex generators on radio controlled aircraft.
jerryd
This is a bunch of bull. I design, build wind generators and high speed sailboats and it's unlikely this will help. They also don't mention the far higher added drag on the rest of the rotation. Just another grant money scam.
Dirk Scott
US patent law is weird. How can you patent something the whales invented millions of years ago?