Humpback whales inspire better helicopter design
Humpback whales are known for their great speed and acrobatic skills due to their unusually large pectoral fins, which have bumps along the front edge. DLR researchers translated the idea of using bumps for delaying the onset of stalling to helicopter rotors and tested it out using the Bo 105 research helicopter.
BERLIN, Germany — The connection between humpback whales and helicopters might not seem obvious. But a group of researchers in Germany are thinking way outside-the-box, applying nature’s design to helicopters to make them faster and more maneuverable.
The team at the German Aerospace Center (DLR), in Goettingen, was eager to solve an aerodynamic conundrum: The airflow over a helicopter's main rotor blade creates a hazard called “dynamic stall.” This causes turbulence, a loss of lift, and exerts extreme pressure on the rotors, ultimately limiting maneuverability and the speed that any helicopter can reach.
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When searching for a way to thwart this stalling, they hit upon the humpback whales. The marine mammal's speed and acrobatic prowess is largely attributed to its large pectoral fins, which have characteristic bumps along the front edge. These bumps, it turns out, significantly delay such stalling.
“This particular shape makes the humpback whale more agile,” Kai Richter, a researcher the DLR Institute of Aerodynamics and Flow Technology, told GlobalPost.
Richter and his team decided to replicate the whale’s bumps on a smaller scale in rubber, which they named Leading-Edge Vortex Generators (LEVoGs). They then attached 186 of them to rotor blades and tested them out in a series of wind tunnel experiments. When these yielded positive results the researchers then decided to try them out in real life test flights.
“The goal was to demonstrate the safety of this approach, because the most dangerous thing you can do to a helicopter is to modify or manipulate the rotor blades,” Richter explained. “The worst case scenario is that the helicopter crashes.”
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The bumps were attached to the Bo 105 research helicopter, which then embarked on its flight, attaining steadily higher altitudes and attempting increasingly riskier maneuvers. “The first reaction of the pilots was that they recognized that the rotor blades behaved differently, the air flow was different with the bumps and without.”
The next stage in the research project will be to develop a measuring system that can be installed in the helicopter, and then to carry out tests both with and without the bumps. “By comparing the measured values of the two different configurations we can then really calculate the effect,” says Richter.
If the results turn out to be positive, then the bumps could be retrofitted on existing helicopters, at little expense. It’s hardly surprising that the helicopter industry is already interested in what the team comes up with. Eurocopter, Europe’s biggest helicopter manufacturer, is waiting with interest for the DLR’s quantitative research into the bumps’ performance. That is particularly gratifying for the researchers, who have already patented their invention.
Richter says that the team would be delighted if their idea was applied in the real world. “Many of these ideas stay inside research institutions because industry says it is too complicated or too expensive to develop products. But LEVoGs are a very easy and very cheap way to suppress dynamic stall on the rotor blade.”
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