Our Earth is teeming with millions of diverse life forms. From the domestic to the feral, bipedal, quadrupedal, insects and reptiles, the natural world hosts an incredible abundance of animalia. The Bumble (Bombus) or Honey Bee (Apis) are among the very few species of animals who can boast to have baffled the minds of mathematicians and physicists alike for centuries. At a glance, the bee appears much too heavy and stout for flight. It’s wings are too small with respect to their round bodies, which already seem poorly aligned with traditional aerodynamic models and pale in comparison with other airborne creatures. Bees, of course, with secrets of their own, turn these impossibilities to trivialities. In recent years, however, with our current physical knowledge and computational advancements, these secrets have been unraveled, and we can now decisively pinpoint the physics of the flight of the bumblebee.
I generalize this blog to the bumble or honey bee, but these physics apply to all bees under the Apoidean superfamily. The basis of bee flight is founded on two core aspects. Firstly, we must directly examine the concept of flight unique to the bee in this case, and how it contrasts other modes of aviation found in birds or airplanes. We have all seen man-made plane wings before, or can imagine the great pinions of an eagle in flight. They are blunt and rounded in the direction of the air flow, designed to make the air flow on top of the wing flow faster than the air on the bottom of the wing. This creates a pressure differential in the air, which is balanced out by an upward force on the wing, which pulls the plane upward. The bee’s wing, on the other hand, is much more akin to a thin foil, and as such, it can manipulate the airflow around its wings, creating tiny tornadoes or vortexes at their tips. These are known as Leading Edge Vortices (LEVs), and are a core factor in the flight of bees, wasps, moths and many other insects.
Figure 1: The effect of the leading-edge vortex.
As can be seen in the above diagram, the Leading edge vortex provides the minibeast with an “induced downwash” of air. This accounts for a major portion of the creature’s weight and offers it a huge amount of stability mid-flight. It is through this method that bees are capable of hovering in place, it is also worth noting that all insects that fly in this manner must beat their wings hundreds of times a second to achieve this feat. This stunning amount of motion in a short time frame is what causes the signature buzz of the bee.
Crucially, these leading-edge vortices allow the bee to maintain a distinct wing path. Rather than just flapping them up and down, the bee is able to follow a curved loop with its appendages. These are not rigid appendages, and can bend and twist at will; this enables not only a way of directional influence in the bee’s flight, but is in fact paramount to the performance of the aforementioned wing path. The LEVs produced at the tips of its wings allow the bee to angle its wings higher against the air, this higher angle ingrained into the wing path provides the insect with enough force to become airborne. There is a delicate yet essential pressure difference again between the top and the bottom of the wing, maintained exactly and constantly by these vortices. (3)
Figure 2 : The wing path of the bee.
In a way, one can see that the flight of a humble bumble bee and a Boeing 747 are (perhaps) not too dissimilar after all. The natural solution to flight is both wonderfully elegant and simple. By means of updrafts, induced downwashes and differences in pressure, advanced aerodynamics, muscle control or jet fuel, the bee, bird and Boeing 747 are all capable of achieving flight in their own unique way.
References : Figure 1): https://doi.org/10.1038/35089159
Figure 2): https://askabiologist.asu.edu/how-do-bees-fly
(3) : https://doi.org/10.1098/rsif.2017.0159
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