THE mysterious lumps on the fins and heads of humpback whales make the
behemoths more manoeuvrable, say American researchers. The finding may inspire
new designs for boats and aircraft.
The lumps, or tubercles, have long puzzled biologists. So Philip Watts of
Applied Fluids Engineering, a company based in Long Beach, California, and Frank
Fish of West Chester University in Pennsylvania tried simulating the effect of
the tubercles on the leading edge of whales’ fins. To their surprise, they found
that the tubercles not only reduce drag by 10 per cent, but also increase lift
by 5 per cent. “It’s very rare to find something that does both at the same
time,” says Watts. “Usually something that reduces drag also reduces lift and
vice versa. Nothing else like it is known.”
The effects seem to be due mainly to the creation of a series of low-pressure
regions across the fin’s upper surface rather than a continuous one. These
regions increase lift, and splitting them this way appears to reduce drag too.
“It’s as if you’re dividing your wing up into different sections,” Watts says.
“It’s counterintuitive—at first we didn’t believe our simulations.”
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Watts and Fish hope that their work could improve the manoeuvrability of
planes. “At the moment, aeronautical engineers think leading edges have to be
straight,” Watts says.
The tubercles help humpbacks make tight turns as they pursue their prey,
Watts told a meeting on comparative biology in Chicago last week. He says it’s
the first evidence that tubercles have a purpose.
George Karniadakis, a fluid dynamicist at Brown University in Rhode Island,
cautions that their simulations may be too simple. “But it’s worth exploring
further. If they are right, it would be easy to implement and could be very
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