In the early 1980s, Frank Fish saw a sculpture of a humpback whale in an art gallery in Boston. He burst out laughing.
When a clerk asked him if something was wrong, Fish said the artist had placed the bumps, called tubercles, on the wrong side of the whale’s flippers. The aptly-named Fish had earned a PhD in zoology a few years earlier, where he specialized in the physics of swimming animals. One of Fish’s professors had often peppered his lectures with critiques of artworks with biological inaccuracies.
But, to his surprise, Fish learned that the sculptor had reproduced the subject faithfully. Fish knew that whales use their flippers like wings, so he had expected them to be smooth, for streamlined flow of water, like airplane or bird wings. Fish spent the next several years trying to find out why humpbacks are different.
Fish discovered that marine scientists viewed the tubercles as a developmental artifact. “The humpback’s flippers are out of proportion to its body compared to related whales, so the thought was tubercles popped out because the flippers were disproportionally large,” Fish said. “No one had considered that they might have a fluid dynamic effect.”
So Fish put his name on the Smithsonian’s waiting list for beached whale specimens, so he could study “the real thing,” and continued his work as a professor of biology at West Chester University of Pennsylvania. After nearly ten years, Fish got a call that a dead humpback whale had washed ashore in New Jersey.
“I didn’t want to get stopped with a trunk full of rotting body parts in New Jersey.”
He found the 30-foot cetacean with 10-foot flippers and spent hours sawing the flippers into thirds by hand, in order to fit them into his Mercury Lynx. Fish told Mechanical Engineering magazine that the weight of the flesh made his small car sag. “That worried me,” he said. “I didn’t want to get stopped with a trunk full of rotting body parts in New Jersey.”
At first, the flippers proved too unwieldy to make a cast and too tough to cut into sections, so they languished for years in a university freezer. Eventually, Fish visited the University of Pennsylvania’s Veterinary School, where he learned of a saw that was powerful enough to cut up large carcasses. He made sections of the flippers and ran them through CAT scans.
Fish’s analysis revealed that the distance between the bumps was consistently 7 to 9 percent of the flipper’s span. After doing fluid modeling, he found the tubercles’ hidden function: they seemed to reduce drag. With Phil Watts, an engineer, Fish presented the findings at a conference in 2001. Laurens Howle, a mechanical engineer at Duke University, was impressed by their research. Howle made a plastic model of a humpback flipper and tested it in the U.S. Naval Academy’s wind tunnel. He proved that the tubercles decreased drag and held off stalling at sharper angles of attack, meaning the whale would be able to get more lift.
Tubercles: Evolutionary advancement
Eventually, Fish came to believe that the tubercles help humpback whales during feeding. Unlike most whales, which filter out plankton from large amounts of water, humpbacks encircle their prey—small fish—by blowing bubbles around them. They hunt in groups and progressively tighten the circle, until they can swallow a dense group of fish in the center. By maximizing lift from their flippers, they can make the sharp turns needed to trap their prey.
Fish told us that some porpoises have similar bumps on their dorsal fins, which seem to make them quieter in the water. This may help them elude their main predators, killer whales, and perhaps will one day help us design better stealth technology. Fish pointed out that there is evidence of tubercles in a group of fishes from the Paleozoic Era, 300 million years ago, and in a swordfish-like animal during the time of the dinosaurs.
“We have seen bumps on hammerhead sharks, and the whiskers of certain seals have oblong cross sections and wavy bumps along their length,” he said. “The bumps get rid of self-induced vibration so the seal can detect small changes in water made by prey.”
In 2005, Fish formed WhalePower, a Toronto-based company, with Watts, Howle and Steven Dewar, an entrepreneur. The small firm has been working on researching and commercializing tubercles. “We have already tested fans and wind turbines, and I’m sure tubercles could be applied to aircraft,” Fish told us.
WhalePower first licensed its technology to Ontario-based Envira-North Systems, which sells large, high-volume cooling fans for barns, warehouses and other commercial and industrial facilities. New fans outfitted with tubercles on the blades are said to move 25 percent more air using half the blades (five instead of the previous 10) and 20 percent less electricity. They can reportedly reduce heating and cooling bills by 20 percent.
The fans have been saving buyers electricity. “I saw a report showing that a farmer with large barns has saved around $100,000 in electricity using the fans,” Fish said, referring to analytics from utility Ontario Power. The lower number of blades also means the manufacturer saves on material and production. “It’s a win for the company and the end user,” he said. “And the fans are quieter.”
WhalePower is also looking at developing a better computer cooling fan, with early testing showing a performance boost of 12 percent with tubercles. On the horizon may be auto and diesel engine fans.
The company is also looking for partners to license the technology for wind turbines. Fish explained that turbine blades could be readily outfitted with fiberglass and composite tubercles in a process akin to filling a tooth, a procedure he says would make the blades stronger, quieter and more efficient. As with a flipper, the modified blades would have less drag and more opportunity for greater lift with less stall.
“It is a novel type of geometry, but once people start to see the utility of it, it will start to become more ubiquitous.”
In 2008, the Wind Energy Institute of Canada tested tubercles on the blades of a 25 kW wind turbine. It found that the modified blades reached full power at 12.5 m/s, compared with 15 m/s for conventional blades, and estimated that they would produce up to 20 percent more electricity annually, depending on wind speed.
WhalePower also licensed its tubercle technology to a company called Fluid Earth, which is working on surfboard fins that allow riders to make sharper cuts through waves.
Fish believes more testing is needed on tubercles, though he is bullish on potential applications. “It is a novel type of geometry, but once people start to see the utility of it, it will start to become more ubiquitous,” he said.
And there’s no doubting the importance of our natural resources when it comes to emulating organic forms, processes, and ecosystems to create more sustainable technology and design.
“It’s ironic that we almost sent whales to extinction, yet they showed us a way we can get more energy out of renewable resources, or do things more efficiently,” Fish said. “It’s critical to protect our oceans and biodiversity, because who knows what is coming from the next jellyfish?”