The alula is a small structure located at the joint between the hand-wing and arm-wing of birds and is known to be used in slow flight with high angles of attack such as landing. It is assumed to function similarly to a leading-edge slat that increases lift and delays stall. However, in spite of its universal presence in flying birds and the wide acceptance of stall delay as its main function, how the alula delays the stall and aids the flight of birds remains unclear. Here, we investigated the function of alula on the aerodynamic performance of avian wings based on data from flight tasks and wind-tunnel experiments. With the alula, the birds performed steeper descending flights with greater changes in body orientation. Force measurements revealed that the alula increases the lift and often delays the stall. Digital particle image velocimetry showed that these effects are caused by the streamwise vortex, formed at the tip of the alula, that induces strong downwash and suppresses the flow separation over the wing surface. This is the first experimental evidence that the alula functions as a vortex generator that increases the lift force and enhances manoeuvrability in flights at high angles of attack.
The alula-TREK is the latest version of the the world's most popular bird-inspired RC glider. The ultra lightweight and packable airframe is perfect for travel and exploration, assembling in minutes without glue! Whether at a a coastal dune, mountain ridge, or your local park- the only limit is your soaring imagination. Spend less time building and more time outside flying, with the Dream-Flight alula-TREK.
Landscape Use and Care: This plant is excellent for those people interested in xeriscape gardens. It thrives in full sun but does O.K. in partial shade. The alula does not like to have continuously wet roots so you should let the soil dry out in between waterings. If the soil is always wet at your home, the alula does fine in a pot. Watch out for red and black flat mites on the underside of leaves they will cause the leaves to become spotty and ugly. Slugs can also do a number on the stem of this plant sometimes eating through it over night so watch out for those little buggahs too.
AlUla Saudi Arabia, 18 October 2022: The Royal Commission for AlUla (RCU) is launching its latest Artist Residency programme in partnership with the French Agency for AlUla Development (Afalula). 041b061a72