The spectacle of the cranes that split the sky in one V formation perfect has something fascinating about it. Although scientists have known for a long time that this configuration offers an aerodynamic advantage, a certain vagueness persisted.
A study published in Proceedings of the National Academy of Sciences by researchers at Brown University sheds light by simulating the forces at play for a bald ibis.
How does the V position reduce flight effort?
The secret lies in the exploitation of wing tip vortexthese mini-tornadoes of air generated by the lead bird.
The researchers’ model demonstrated that a well-positioned tracking bird benefits from an 11% reduction in the mechanical power required for flight. This saving mainly comes from decrease in vertical amplitude wingbeats.
” The big change we see in this position is in the amplitude of the beat. We are talking about an amplitude that is about 70% of what it would be if the bird was flying alone. That’s a pretty dramatic change. “, souligne Olivia Pomerenk.
Is this a gain in lift or thrust?
For a long time, the theory was that the follower bird rode the updraft created by its leader to gain lift. However, the new model qualifies this vision.
” If I am a bird in flight, I have two problems to solve. I have to generate lift to counter gravity, and I have to generate thrust to move forward. “
The model shows that the lead bird’s wake especially helps with pushing. By receiving this help, the follower bird can reduce its own effort to move forward, which results in less ample and more economical wing beats. The bird only needs to produce 83% of the thrust of a solitary bird.
Beyond the case of birds
This refined understanding of formation flying has applications well beyond the avian world. The physics brought to light could be used to optimize the functioning of systems designed by man, and better operate drone swarms in agriculture or firefighting.
