Shinkansen TrainUpdated: 07/25/2012
High speed train silently slices through air
About the ProductCompany: Japan Railways Group
Product Phase: Available
Product Type: High speed train
Product or processThe Shinkansen Bullet Train has a streamlined forefront and structural adaptations to significantly reduce noise resulting from aerodynamics in high-speed trains.
In Japan, the
500-series bullet trains could travel 300 km/hour (200 mph) but the sound
levels exceeded environmental standards. One source of noise was an atmospheric
pressure wave forced in front of the train as it traveled through a narrow
tunnel, creating a sonic boom at the exit. The bullet-shaped nose was part of the problem. Another source of noise was the pantograph, a
protrusion that extends above the train to receive electricity from wires
overhead. The structural adaptations of the Shinkansen train help to minimize these concerns.
Differences from existing productsThe more streamlined Shinkansen train not only travels more quietly, it now travels 10% faster and uses 15% less electricity.
The biomimicry story
Eiji Nakatsu, an engineer with JR West and a birdwatcher, used his knowledge of the splashless water entry of kingfishers and silent flight of owls to decrease the sound generated by the trains.
Kingfishers move quickly from air, a low-resistance (low drag) medium, to water, a high-resistance (high drag) medium. The kingfisher's beak provides an almost ideal shape for such an impact. The beak is streamlined, steadily increasing in diameter from its tip to its head. This reduces the impact as the kingfisher essentially wedges its way into the water, allowing the water to flow past the beak rather than being pushed in front of it. Because the train faced the same challenge, moving from low drag open air to high drag air in the tunnel, Nakatsu designed the forefront of the Shinkansen train based on the beak of the kingfisher.
Engineers were able to reduce the pantograph's noise by adding structures to the main part of the pantograph to create many small vortices. This is similar to the way an owl's primary feathers have serrations that create small vortices instead of one large one.