From: David A Gabel, ENN
Published September 10, 2010 10:45 AM

Flying Fish Aerodynamics

There is widespread knowledge of airborne creatures taking to the water. Everybody knows about ducks and geese, penguins, and seabirds that dive for their prey. But, there is scant attention for the seaborne creatures that take to the air. Flying fish really do fly. A new study published in the Journal of Experimental Biology takes a look at how these amazing animals do what they do.

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Flying fish, from the family of marine fish, Exocoetidae, can remain in the air for over forty seconds and cover distances of 400 meters at speeds of 70 km/hr (43 mph). There are about 64 species which all live in oceans at the tropical and subtropical latitudes. There pectoral fins are enlarged, allowing the fish to take flight to escape predators by leaping out of the water. Their "wings" have an aerodynamic shape that can be compared to those of birds.

The study by Haecheon Choi and Hyungmin Park of the Seoul National University in Korea went about to find out how fish can stay aloft. First, they had to catch the fish for his experiments, which proved to be quite difficult. After selecting five similar-sized fish, Park had them dried and stuffed, some with their wings extended as if in flight. These were then taken to the wind tunnel to test their aerodynamics.

Like any aircraft, the fish have a lift-to-drag ratio that is essential to flight. The researchers found that it actually quite good, gliding better than insects and as well as some waterfowl. The fish are not as good at turning, however. They fly best when their wings are parallel to the surface of the water.

When the wings were swept back, the flight became more unstable, but that is what is necessary for aquatic aerodynamics. This makes the flying fish well adapted in both environments.

The researchers realized that flying fish always glide just above the surface of the sea, never at a high elevation. Therefore, they tailored some of their wind-tunnel experiments so that the fish was set up near the floor. They found that the lift-to-drag ratio rose as the elevation became less and less. The fish can go farther by staying closer to the water.

The next step for these intrepid researchers is to construct an airplane inspired by the design of the flying fish. Now that would be a sight to see.

For more information: http://jeb.biologists.org/

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