动物实验 z-bo 2020-09-28 402

　　By analyzing the Lagrangian coherence structure (Lagrangian coherence structure) of the surrounding water when the fish swims, the scientists clarified the physical mechanism of the fish swimming in the water. This research method is very useful for aircraft flight dynamics and other complex fluid flows.

　　It is said that fish can swim freely in the water, but when you twist your body and see the ripples remaining in the water, you will find that everything is not as easy as it sounds. The fish must constantly exchange energy with the surrounding water. Due to the nature of continuous flow of large amounts of water, it is difficult to quantitatively calculate this energy conversion to generate the power to swim them.

　　For objects that are separated from each other, it is usually easier to calculate the interaction between the two. For example, when studying the movement of skiers, the distance between the skier and the slider is so far that researchers can easily calculate their interaction. However, due to the continuity of water bodies, it is difficult to calculate the interaction between fish and water. It is difficult to determine which part of the swimming fish played the most direct role in promotion.

　　Recently, a Swiss research team discovered that by breaking the body of water into a series of independent vortices, it is possible to study the movement of fish swimming in the water. Their technology will also benefit from other fluid mechanics research, such as the study of unstable air vortices separated from wings. The results of the research team were published in a journal published by the American Physical Society on June 23. "chaos".

　　In a series of simulation experiments, the researchers focused on the water vortex closest to the fish. "I believe these vortices play an important role in the fish swimming in the water. The fact that these currents are spinning emphasizes the strong interaction between the fish and the water. "We do. "Project leader Florian Hong said.

　　"This is a closed curve around these water vortices," Huon said. "Once we know the boundaries of these curves, we can study the mechanism of how a closed body of water promotes fish swimming." By identifying the structure of the water body, the continuous flow of water becomes independent. Separate into individuals, which allows more. The interaction between the water body and the fish body is well calculated.

　　The research team conducted a simulation study on the swimming patterns of two fishes. The first is smooth exercise, that is, regular wave swimming. The other is to call the escape reaction (escape reaction) C start. In other words, you can quickly bend the fish's body into a "C" shape, then flip it outward and swim quickly. Researchers found that when the fish moves smoothly, swimming is mainly due to the momentum exchange between the fish's body and the various water vortices. In the case of the initial reaction of C, the water vortex can also explain its movement mechanism well, but "there is also a non-rotating water flow area surrounded by the vortex area, which also plays a role in the fish swimming mechanism. This is very important character of."

　　Huhn believes that their method is also useful for fluid analysis. "When an object (such as a bird in the sky or an underwater fish) moves forward in a fluid (such as an airplane, a ship or an airplane), vortices are generated. Using our method, these vortices are formed. You can recognize and understand them Evolution," he said. "Our findings also confirm the effectiveness of the Lagrangian quasi-sequence structure in dividing unstable fluids into dynamic discrete regions."