Millions of years of evolution have give birds techniques for flying with a grace of God that locomotive engineer have yet to match . One of these chef-d’oeuvre of aerodynamics has now been explained by learn the mechanism of their alula , a social organization at the bend of the wing that helps razzing turn and land more gently .
Although the alula also run low under the unflattering name of “ bastard annexe , ” the 2 - 6 feathering that sprout from the doll ’s adapted ovolo areknown to play a role in flight . As a feature film thatdates back to fly dinosaurs , its value is not in question . However , that does n’t mean we eff precisely what that time value is , allow alone how we can use it to our own forms of flight .
Structure of a distinctive bird wing with the calypter in red . Credit : Muriel Gottropvia Wikimedia Commons .
" It ’s not that [ birds ] can not fly without the alula . " saysDr . Sang - im Leeof Seoul National University . " But with the alula they seem to turn more easily . "
A newspaper publisher inScientific Reports , on which Lee is lead author , note : “ The spurious wing … is known to be used in slow flight with high-pitched Angle of attack , such as landing . However , in nastiness of its general comportment in flying birds and the wide acceptance of stall delay as its main function , how the calypter delays the stall and help the flying of bird stay unclear . ”
Lee used a combining of footage of puerile magpie ( Pica pica ) in steep descent before and after shed their calypter feathers as well as malarkey burrow experiments with annexe from dead birds . “ When the alula was present , the continuance of total descending flight was little , ” the paper report . “ Our result suggest that the use of alula should activate the bird to perform steeper descending flights with groovy change in body preference . ”
The wind tunnel experiments suggested that the airflow separated further back from the border of the wing when the alula was present . Lee and co - source attribute this to “ a vortex [ take shape ] at the tip of the alula feather . ” This , in go , created vortices downstream .
The paper admit that it is still not clear how the calypter inhibit flow separation at steep angles , although it provides a potential explanation . Nevertheless , “ The alula - crown swirl is the cardinal chemical mechanism for lift sweetening and sales booth hold , ” the authors conclude .
" Nature is full of whirlpool , and the animals and plants apply them wisely . The role of the bastard wing in avian flight of steps is just one example,“saysco - author Dr. Haecheon Choi .
The vortices that appear over the calypter change the airflow over the annex , allowing birds to land steeply without stall . Credit Lee et al . , Scientific Reports .
