Flying fish glide as well as birds
We’re all familiar with birds that are as comfortable diving as they are flying but only one family of fish has made the reverse journey. Flying fish can remain airborne for over 40 seconds, covering distances of up to 400 m at speeds of 70 kph.
Haecheon Choi, a mechanical engineer from Seoul National University, Korea, became fascinated by flying fish when reading a science book to his children. Realising that flying fish really do fly, he and his colleague, Hyungmin Park, decided to find out how these unexpected aeronauts stay aloft…
Fitting 6-axis force sensors to the fish’s wings and tilting the fish’s body at angles ranging from –15 deg to 45 deg, Park and Choi measured the forces on the flying fish’s fins as they simulated flights.>> [Using dried, stuffed fish BTW]
Choi and Park found that the flying fish performed remarkably well: gliding better than insects and as well as birds such as petrels and wood ducks…Knowing flying fish always fly near the surface of the sea, Choi and Park then decided to find out if the fish derived any benefit from the aerodynamic effect of flying close to the surface.
Lowering the fish’s height in the wind tunnel they found that the lift-to-drag ratio increased as the fish models ‘glided’ near the floor. And when Park replaced the solid surface with a tank of water, the lift to drag ratio rose even more, allowing the fish to glide even further. So, gliding near the surface of the sea helps the fish to go further.
Finally, Choi and Park directly visualised the air currents passing around the flying fish’s wings and body. Blowing streams of smoke over the fish, the duo saw jets of air accelerating back along the fish’s body. Park explains that the tandem arrangement of the large pectoral fin at the front and smaller pelvic fin at the back of the fish’s body accelerates the air flow towards the tail like a jet, increasing the fish’s lift-to-drag ratio further and improving its flying performance even more.
Having shown that flying fish are exceptional fliers, Choi and Park are keen to build an aeroplane that exploits ground effect aerodynamics inspired by flying fish technology.
Anyone in the Caribbean could have explained that flying fish are at least as fast and efficient as birds.
And they taste absolutely superb. Drying and stuffing them should happen after the meal.
