To the brave bird willing to wear goggles and fly through a laser sheet: we salute you. Thanks to you, we know a little more about how you and your kind fly.
When birds lift off, their wings generate 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 fly, but 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 to record a small parrotlet named Obi flying through the laser. This let them visualize the wingtip vortices — and they found that the actual 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 laser sheet 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. When something (like a bird) goes through the wind tunnel, its movements disrupt the particles, and the laser helps you see how the particles move now.
Of course, none of this would work 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 the full-size goggles that the scientists use themselves.
Next, they trained the bird to fly between perches in the wind tunnel while wearing the goggles. Considering all the bird got 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 down after only about three wingbeats, which isn’t what formulas would have predicted. We’ve see this pattern in airliners but never in birds, so this suggests that some of our ideas about bird flight might lift off.
In other words: this bird has done a great service to science.