How one engineer's birdwatching made Japan's bullet train better

What is the connection between an engineer going bird watching and his saving millions of dollars for his company?

Or, what does catching flies have to do with preventing plane crashes? How will locust swarms change the nature of our highways? Can a mold do a better job of plotting our mass transit systems than a team of engineers and planners?

The common thread in all these scenarios: Deep observation and analysis of the natural world can lead to amazingly creative innovations. I will write about all these things in this series on transportation, but first let’s take a look at a how a couple of interesting birds inspired a sleek design.

Eiji Nakatsu was the general manager of the technical development department for the so-called “bullet” trains of Japan, famed for their speed and safety record. After attending a 1990 lecture on birds by an aviation engineer, Nakatsu, who is also an engineer, realized studying the flight of birds could bring his train, and us, into the future.

The Sanyo and Kyushu Shinkansen Lines, operated by Japan Railway West, connect western Japan’s two biggest cities, Osaka and Fukuoka, and are an extension of the older Tokaido Line from Tokyo to Osaka.

The 515-kilometer Tokaido Shinkansen is the world’s busiest high-speed-rail line, having moved 4.9 billion passengers from its opening in 1964 (for the Toyko Olympiad) to 2010. Indeed, more people move by train in Japan  -- an estimated 64 million a day -- than anywhere else in the world.

Making his trains faster was one of Nakatsu’s goals, but to do that, he needed to first make them quieter. The trains ran through dense neighborhoods and many tunnels. The loudest noise came from the connections to overhead wires (pantographs), and the emergence of the trains from the tunnels on the line. This dynamic was so forceful that it was creating sonic booms heard by residents 400 meters away.

In the case of the pantograph noise, air rushing over the struts and linkages in the mechanism was forming into so-called Karman vortices, also known as a Karman vortex street, and this turbulence was causing most of the noise. Karman vortices are created at all scales, from islands in the ocean to car aerials, and are manifested wherever a single bluff body separates the flow of a fluid. Alternate and opposite eddies swirl downstream of the obstruction, swinging back and forth as the force of one dominates and then the other.

Next page: How owls fight turbulence