At the graduation design exhibition of the first batch of graduates of aerospace engineering, Zhao Yingxue's design project was unique and eye-catching. She tried to apply the shark skin small tooth structure on the wing of the aircraft, do not underestimate this seemingly amazing small tooth structure, it can not only play a role in reducing resistance and saving fuel, but also achieve carbon dioxide emission reduction and promote the development of green aviation.
Zhao Yingxue
At present, the problems encountered by the aviation industry are mainly environmental protection issues and economic problems. Carbon dioxide (CO2) and nitrogen oxides (nox) produced by aero engines have a very adverse impact on the atmospheric environment, and aviation fuel efficiency directly affects the economic efficiency of airports. Therefore, how to achieve economical and green aircraft design is the trend of the times. Zhao Yingxue, a senior in aerospace engineering, seized the bottleneck of the aviation industry and decided to improve the performance of the aircraft by improving the shape of the wing in her graduation design.
In aircraft design, the wing is an important part because most of the lift and drag comes from here. The lift comes from the pressure difference between the upper and lower surfaces of the wing under the action of the air flow, while the resistance mainly comes from the rotation of the air flow in the boundary layer of the wing surface, and the air flow is rotated from the initial laminar flow under the action of the reverse pressure gradient and converted into turbulence. Since turbulence has greater surface friction resistance, we also wanted to prevent turbulence from occurring to the greatest extent possible in the design of the wing. Dr. Dinesh Bhatia, Zhao Yingxue's mentor, who studies the application of biomimicry to structural surfaces, gave her some inspiration, and perhaps she can find the answer in nature.
Long before the advent of humans on Earth, various creatures had lived in nature for hundreds of millions of years, acquiring the ability to adapt to nature in the long evolution of their struggle for survival. For example, bats and radar echolocation pathfinding; Bees and buildings, cameras, artificial satellites, polarizers; Birds and airplanes. Inspired by birds, humans not only invented airplanes, but also improved their various performances. The above four cases are thought-provoking and also greatly inspired Zhao Yingxue.
In the field of fluid mechanics, she learned that the structure of shark skin has certain drag reduction properties for sharks when swimming in the sea. Shark skin is not as smooth as most people think, but has a variety of small tooth structures like fish scales. These small teeth change the properties of the fluid as it passes through the shark, making the shark one of the fastest species to swim in the sea. The speedo fast-skin swimsuit designed by the scientists using the shark skin structure greatly reduces the resistance of swimmers in the water, helping them swim faster. American swimmer Michael Phelps won 8 gold medals in this swimsuit at the 2008 Beijing Olympic Games. Therefore, under the advice of her mentor Dr. Dinesh bhatia, Zhao Yingxue began to try to apply the small teeth on shark skin to the wings to achieve the effect of reducing drag.
After querying a large amount of data and research calculations, Zhao Yingxue first determined the physical model size that can be experimented on engineering technology according to the mathematical model through the study of biological prototypes, determined the size and then cad modeled the shark skin tooth structure, Yingxue imported these built models into ansys fluent software, through computational fluid dynamics (cfd) simulation to find the role of shark skin in aerodynamics, and by constantly adjusting the position and angle of the small teeth, Find the optimal drag reduction solution.
During the simulation, she found that when the air flow passes through the shark skin teeth, a separation bubble is generated behind it, which accelerates the air flow by separating and pasting back, so that the air flow is closer to the surface of the wing, so that the air flow is closer to the laminar flow, and the flow can be postponed into turbulence, reducing frictional resistance. And the shark skin small tooth structure will create a low pressure zone, and the pressure difference caused by the low pressure zone will also offset some of the resistance. Through simulation calculations, Zhao Yingxue found that compared with traditional wings, shark skin can reduce the resistance of the aircraft by 4% and increase the effect of raising the resistance ratio by 4%. Although it may seem like a small value, it would save a lot of fuel for such a large aircraft.
Carrying out such a complex and exquisite graduation design not only relies on Zhao Yingxue's diligent efforts, but also inseparable from her love for aerospace. Zhao Yingxue's father is an engine engineer, and under the influence of her father, she has developed a strong interest in airplanes. While preparing for the college entrance examination, she was pleasantly surprised to find that the University of Nottingham Ningbo China was about to open an aerospace engineering major, and it was ranked high in the world at the UK campus. It is a great pleasure for her to study at a school that can both receive a diversified educational model and learn the knowledge she is interested in.
In the four years of university study, Zhao Yingxue has always maintained a high enthusiasm for learning. Her grades have also been among the best. Of course, in the four years of study, there are joys and gains, but there are still difficulties and setbacks. Among them, the most headache for Yingxue, and the biggest benefit for her, is the ability to solve problems and learn independently. Zhao Yingxue said: "I think if you want to be a qualified engineer, you have to start from college to cultivate the ability to solve problems independently. ”
In her graduation project, the CAD software and cfd software used in modeling and meshing will encounter a variety of problems, and these problems are difficult to find directly on the Internet. When encountering problems, she often carefully compares various parameters, confirms them repeatedly, and finally excludes and solves some problems that may lead to errors. She then searches through a lot of relevant materials to try to solve the problem herself. "Although the process was boring and very painful, I felt very happy when I solved this problem through my own ability. Of course, if there is a problem that cannot be solved, don't dwell on it for too long, or turn to teachers with more experience! ”
Unnc's diversified educational experience is also a valuable asset that Zhao Yingxue harvested in Ningnuo. "I am very grateful to the teachers for their guidance, nurturing and selfless help on the learning path," she said. Ningnuo's international teaching team allows us to experience a variety of teaching methods. We can adapt our learning style to our needs, and we can manage our time and learn knowledge more effectively. In addition, unnc has made me make many international teachers and friends, allowing me to understand and experience the customs and cultures of different countries. I believe that these are unique to our school and are a valuable asset for unnc teachers and students. ”
In the future, Zhao Yingxue hopes that she can go further in the design of green and energy-saving aircraft, and continue to study in the field of active and passive flow control. In December of last year, she received her acceptance letter from Imperial College, famous for her engineering degree in Advanced Master of Science in Aeronautical Engineering, to continue her studies.