Since the birth of aerodynamics, scientists have noticed that the flight of insects is a bit strange. Early studies show that insects fly by flapping their wings quickly, but this force is too small. According to the ratio of their weight to flight power, it is impossible for scientists to build human planes.
1934, scientists Antoine Manley and Andre Sanchez studied the flight of bees. They used mathematical analysis and known flight principles to calculate the flight of bees, and reached the conclusion that "bees can't fly" in theory. Since then, bees have become a typical example of not obeying aerodynamic principles.
Scientists define it this way because they can't make an airplane with flashing wings. It is inconceivable that human beings can produce 300,000 times respiratory efficiency.
The origin of insect flight can be traced back to the Paleozoic at least 350 million years ago, when the earth was full of swamps. Swamp is also an ideal paradise for insects, so at that time, the earth was full of insects, but they all had no wings. At that time, they didn't need such complicated things. Matthew Douglas, a world-famous entomologist at the University of Kansas, proved that insects at that time only had wings, which were small protrusions similar to wings that grew on the chest of insects, also called pendants. Their function was originally to absorb the heat of the sun, which can raise the body temperature of insects when the temperature drops.
In the Paleozoic Carboniferous, there was a dramatic scene: amphibians and reptiles began to land in large numbers, and they all ate insects. In this way, in addition to the original natural enemies spiders and scorpions, insects have a third deadly enemy. At first, insects escaped the attack of amphibians by jumping. Fortunately, the pendant on the insect's chest can make them fly, although the distance is short, it is enough to keep them alive.
Based on the evolutionary law of survival of the fittest, the wings of surviving insects gradually began to develop and gradually formed the embryonic form of wings. Entomologists speculate that some insects will flap their small wing pendants when they run for their lives, so that they can glide further. Finally, these pendants developed into beautiful wings and unfolded. Insects flap their wings with strong chest muscles, so they can fly far away, and carnivores can't reach them.
Boeing 747 can fly like an insect without flapping its wings. This is because it uses 350 tons of explosive energy and has made enough efforts in airfoil design, so it can get great lift. If the plane flaps its wings like a bird or an insect, there will be air vortex around it, which will cause stall and fall.
For a butterfly weighing only 0.056 grams, its flight mode cannot be explained by this theorem. If it is explained by fluid mechanics, it will also come to the conclusion that "insects will fall".
It was not until 1998 that Professor Richard Huntington of Cambridge University in England clearly explained the difference between the flight modes of airplanes and insects. The secret lies in the magical whirlwind.
What is air? Air is not as cold as you think, but it has both volume and quality, and it is also something with a certain viscosity. For example, when riding a roller coaster, the whole body will lean back because of the wind pressure. The light white butterfly will suddenly run out of energy when taking off. Then it will stir the sticky air with its muscles, making the air around its wings swirl, and through the reaction force it generates, it can fly upwards with the help of the power of spiral airflow. When the wings flap from top to bottom, the body floats upward, and when the wings are lifted, it begins to fly forward. This situation and reason are very similar to human disc swimming.
In order to reveal the flight mystery of bees and other insects in more detail, Professor Huntington's team spent nearly a year making a slightly larger mechanical moth, whose wings are powered by miniature batteries, and the fan power and angle are basically the same as those of real moths. The researchers put it in a wind tunnel, and then took three-dimensional photos of smoke moving on its wing with an ultra-high-speed camera. Some unknown details make everyone shine-moths, bees and other insects will produce a sharp spiral air mass at the leading edge of their wings when they take off, which will bring them extra lift.
After carefully watching the three-dimensional image, the researchers found that when the insect vibrates its wings downward, the airflow rises above the wings and forms a series of cylindrical cyclones at the leading edge of the wings. This cyclone is a conical spiral, and the spiral at the root of the wing is very small. The more you reach the tip of the wing, the bigger the spiral is.
The whole cyclone is flush with the leading edge of the wing and close to the leading edge. From the wing root to the wing tip, the intensity of this cyclone gradually weakens and disappears, and then it is replaced by another newly generated cyclone. After the cyclone moves to the tip of the wing, it extends to the tail of the insect and repeats itself, so that the cyclone generated by the vibration of the two wings constitutes a ring. Every time an insect flaps its wings, it will form a cyclone at the leading edge of the wings and then rush out. At this time, its wings are wrapped in the air, but the cyclone formed by the next vibration of its wings once again provides it with the power to take off.
Professor Huntington said excitedly that the flight test proved that this cyclone created a low-pressure area above the wings of insects, and the wings in the center of the low-pressure area would be attracted to rise under the impetus of the surrounding high pressure. Each low-pressure area will be lifted by the surrounding high-pressure area, so that insects in the low-pressure area can gain lifting force.
In the past, aerodynamists suspected that the leading edge cyclone generated by insects flapping their wings could get enough upward force, because they didn't see the details of the cyclone, so they were too conservative.
The discovery of Huntington's team won the recognition of academic authority. They believe that the significance of this discovery is that it is the first time to prove that the cyclone at the leading edge of insect wings is spiral and advances conically from the wing root to the wing tip. This movement keeps the whole cyclone stable, delays the separation between the cyclone and its wings, and enables the cyclone to provide upward thrust for insects as long as possible.
Before revealing the mysterious cyclone, Huntington also explained why insects fly for a long time without fatigue. It turns out that most insects have 8 to 10 pairs of valves in their chests, which are also called breathing ports. Although they don't have lungs and don't need hemoglobin, they can deliver oxygen directly to muscles. This supply efficiency is actually 300 thousand times that of human beings. Therefore, they can flap their wings easily for a long time.
Small insects do contain big secrets. Huntington and experts in the circle know that understanding cyclone and muscle oxygen supply is only the initial stage, and there are still many mysteries to be explored in insect flight. For example, scientists can't explain how insects control their posture in the air because they don't stand still in the air. In addition, how do they cope with changes in wind direction and speed? It is undoubtedly very complicated and difficult to understand how insects control and adapt to these external conditions. Huntington has admitted many times that this obviously cannot be solved by one or two generations, and it needs the combination of multiple disciplines and the development of mainstream science.