The Nearly Effortless Flight of the Albatross

Tuesday, July 30th, 2013

The wandering albatross (Diomedea exulans) travels long distances over open water with no thermal updrafts through a process of dynamic soaring:

Just watch an albatross, and you can easily discriminate its four phases of flight: There’s a windward climb, then a curve from windward to leeward at peak altitude, then a leeward descent, and finally a reverse turn close to the sea surface that leads seamlessly into the next cycle of flight.

Albatross Dynamic Soaring

Students of the albatross’s flight understood early on that the bottommost layer of wind blowing above any surface, including that of water, will incur friction and thus slow down. This layer itself then becomes an obstacle that slows the layer just above it (though not by much), in a process that continues upward. The result is a 10- to 20-meter-high region known as a boundary layer or shear wind field, through which the wind speed increases smoothly and dramatically the higher you go in the field. Dynamic soaring maneuvers extract energy from that field, enabling the albatross to fly in any direction, even against the wind, with hardly any effort.

(Hat tip to Jonathan Jeckell.)

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