10/07/18 14:30:38
つづきです
Why is a fish much more efficient at moving through the water than a ship with a propeller?Well,
a propeller creates a long spinning stream of water called a vortex that stretches behind the ship,
robbing energy and slowing the ship down.
But the flapping tail of a fish is quite different.As it sweeps to one side, it creates (say) a clockwise vortex.
The next step is the key to the efficiency of the fish.
The anticlockwise vortex runs into the clockwise vortex and when they meet they force water away from the fish.
Newton said, 'For every action theis is an equal and opposite reaction', and so, if the water is forced backwards,
there's a reaction that pushes the fish forwards.
Because of this marvelously simple mechanism, fish use hardly any energy to move through the water.
Even an early artificial fish like Charlie the Robofish can achieve 86 percent efficiency, while the best that
our ships can achieve is 40 percent. Of course, fish use extra tricks besides just flapping their tails.
They also flex their bodies, so they can even extract energy out of the vortexes that roll down the
sides of their bodies.However,making an exact copy of a fish,with a smooth and flexible body,is way
beyond what we can build into the robots of today.
長いですがよろしくお願いします！
間違っていたらごめんなさい