For the brave birds willing to wear goggles and fly through a laser sheet: we salute them. Thanks to them, we know a little bit more about how the bird clans stays afloat in the sky.
When birds lift off, their wings produce tiny, circular currents of air called wingtip vortices. Think of them like tiny tornadoes under the wings. The movement of the vortices can tell us a lot about how flapping wings help birds move around the air, however, we weren’t able to measure the currents until now.
In a study published today in the journal Bioinspiration & Biomimetics, researchers at Stanford University used four cameras for recording a small parrotlet flying through the laser. (Sadly, no word on the bird’s name.) This let them visualize the wingtip vortices — and they found that the real way the air moves is different from what we thought based on theoretical calculations. The results might help us build better planes.
One way of visualizing airflow is by using a grid of laser in a wind tunnel. First, you release some particles in the wind tunnel. These particles are supposed to move exactly with the natural airflow. Then you add a laser that illuminates the particles. As something (like a bird) goes through the wind tunnel, its movements disrupt the particles, and the laser helps you see how the particles move.
Of course, none of this will happen unless you find a willing bird. Flying through a laser is no joke either — it could blind the bird.
So the scientists made 3D-printed laser goggles for the bird. The lenses came from a human size goggles that the scientists use themselves.
Then, they trained the bird to fly between perches in the wind tunnel while wearing the goggles. Considering all the bird requested in return were a few seeds, seems like the scientists got a pretty sweet deal. Finally, they recorded everything on high-speed video.
They found that the little “air tornadoes” broke apart after only about three wingbeats, which isn’t what formulas would have predicted. We’ve seen this pattern in airliners but never in birds, so this suggests that some of our ideas about how birds fly might lift off eventually.
In other words: this bird has done a great service to science. And not to mention the entire human race!