Page 120 - Biomimetics: Technology Imitates Nature

Biomimetics: Technology Imitates Nature

even to the naked eye, which other birds lack. These serrations generate
small vortexes in the air flow. Aerodynamic noise stems from vortexes
forming in the air flow. As these grow in size, the noise increases. Since
owls’ wings feature many saw-toothed projections, they form smaller vor-
texes instead of large ones, and the owls can fly very quietly.
When Japanese designers and engineers tested stuffed owls in a
wind tunnel, they once again witnessed the perfection of these birds’
wing design. Later, they succeeded in efficiently reducing train noise by
using wing-shaped pantographs based on the principle of the owl’s ser-
rations. Thus the pantograph system developed by the Japanese, inspired
by nature, became the quietest functioning. 81

The Kingfisher’s Dive and High-Speed Trains’ Entry into Tunnels
The tunnels on the lines used by high-speed trains represented an-
other problem for engineers to solve. When a train enters a tunnel at a
high speed, atmospheric pressure waves rise up and gradually grow up
to be like tidal waves that approach the exit of the tunnel at the same son-
ic speed. At the exit, the waves then return. At
the tunnel’s exit, part of the pressure waves
is released with a sometimes explosive
noise.