The beak of kingfishers allows splashless entry into water due to the wedge shape it makes with the head that is round in cross section.
"[W]e had another challenge that we pursued to the test run phase. Half of the entire Sanyo Shinkansen Line (from Osaka to Hakata) is made up of tunnel sections. When a train rushes into a narrow tunnel at high speed, this generates atmospheric pressure waves that gradually grow into waves like tidal waves. These reach the tunnel exit at the speed of sound, generating low-frequency waves that produce a large boom and aerodynamic vibration so intense that residents 400 meters away have registered complaints. For this reason, we gave up doing test runs at over 350 km/h.
"Then, one of our young engineers told me that when the train rushes into a tunnel, he felt as if the train had shrunk. This must be due to a sudden change in air resistance, I thought. The question the occurred to me - is there some living thing that manages sudden changes in air resistance as a part of daily life?
"Yes, there is, the kingfisher. To catch its prey, a kingfisher dives from the air, which has low resistance, into high-resistance water, and moreover does this without splashing. I wondered if this is possible because of the keen edge and streamlined shape of its beak.
"So we conducted tests to measure pressure waves arising from shooting bullets of various shapes into a pipe and a thorough series of simulation tests of running the trains in tunnels, using a space research super-computer system. Data analysis showed that the ideal shape for this Shinkansen is almost identical to a kingfisher's beak.
"I was once again experiencing what it is to learn from Nature, seeing first hand that a solution obtained through large-scale tests and analysis by a state-of-the-art super-computer turned out to be very similar to a shape developed by a living creature in the natural world. The nose of our new 500-Series Shinkansens has a streamline shape that is 15m in length and almost round in cross section.
"This shape has enabled the new 500-series to reduce air pressure by 30% and electricity use by 15%, even though speeds have increased by 10% over the former series. Another benefit has been confirmed through a favorable reputation among customers that these trains give a comfortable ride. This is due to the fact that changes in pressure when the trains enter tunnels are smaller." (Japan for Sustainability 2005)
Learn more about this functional adaptation.
- Japan for Sustainability. 2005. Shinkansen Technology Learned from an Owl? The story of Eiji Nakatsu. Japan for Sustainability Newsletter [Internet],
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