Peking University Wei Shen struck and solved the problem that the six doctors had not solved for four months in one day

Reports from the Heart of the Machine

Editing: Zenan, mayo

Wei Dongyi: It's too simple, there's no need to ask for money.

Research in the field of basic science is always obscure, but we can often see the meaning of it in some "small things".

On May 6, a screenshot of a WeChat chat sent Wei Dongyi, an assistant professor at Peking University, to a hot search again:

Image source: Weibo @Thief Fork

According to this screenshot, a technology company used PS5 to make a cluster to simulate the physical performance of the product, but as the model becomes more complex, the higher the simulation distortion becomes. The team, which included six PhDs, spent more than four months unable to resolve it, speculating that it was because there was "a problem with the handling of Navistokes' equations" but was unclear what was wrong.

Later, they asked Wei Dongyi for help. After Wei Dongyi sent all the equations, the team spent a day debugging successfully, and the matching rate with the real experimental data in the past was as high as 99.8%.

The end of the story is: Wei Dongyi refuses to accept the remuneration, saying that "it is too simple, there is no need to ask for money", and finally the company gives Wei Dongyi a municipal bus card...

After listening to this process, some netizens said: "This ending is too magical, there is a feeling of watching the network cool article."

Simple and unpretentious

Wei Dongyi's initial unintentional "popularity" was also due to a hot search.

In May 2021, when some media visited the campus of Peking University, they interviewed Wei Dongyi. In the interview video, Wei Dongyi holds a 1.5L bottle of mineral water and carries two steamed buns packed in plastic bags, and his simple image once aroused heated discussion, known as "Wei Shen" and "Sweeping Monk of the Mathematics Department of Peking University".

Wei Dongyi was promoted to the Affiliated Middle School of Shandong Normal University in 2007. In his freshman year, he participated in the 49th International Mathematical Olympiad (IMO) and won the gold medal with perfect marks. In 2009, when he was a sophomore in high school, Wei Dongyi participated in the 50th International Mathematical Olympiad and won the gold again with full scores.

In 2010, Wei Dongyi was escorted to Peking University to study, after graduating from peking university in 2014, he studied for a master's degree and a doctorate at Peking University, after graduating with a doctorate in 2018, he worked as a postdoctoral researcher at the Beijing International Center for Mathematics Research; and in 2019, he was hired as an assistant professor at Peking University. His doctoral thesis, "Axisymmetric Navier-Stokes Equations and the Non-Viscosity Damping Problem", was named the Outstanding Doctoral Dissertation of Peking University in 2018.

According to legend, in order to recruit Wei Dongyi, Harvard University once proposed that it could exempt him from the English test, but the latter refused. Wei Dongyi said that he "does not like to go far away, especially during the epidemic, if some academic conferences can be attended online, then I will participate online." In addition to doing math, he likes to listen to the news and comments on the radio, and pays attention to the number of confirmed COVID-19 cases announced by the Health Commission every day.

At present, Wei Dongyi's mathematical research focuses on analysis, partial differential equations and stochastic matrices.

In 2021, when Wei Dongyi won the Dharma Academy's Green Orange Award, his defense theme was turbulence problems and flow stability problems, and the two original mathematical methods he proposed solved a series of important public problems in the field of flow stability.

Physicist Feynman once said that turbulence may be the last unsolved puzzle in classical physics.

The NS equation: the cornerstone of fluid mechanics

Numerical simulations of fluid mechanics are important for modeling a variety of physical phenomena, such as weather, climate, aerodynamics, and plasma physics. Usually , fluids can be described using Navier-Stokes equations (NS ), but solving such equations on a large scale is still a challenge , limited by the computational cost of solving the smallest spatiotemporal feature.

It was founded by the French engineer and physicist Claude-Louis Navi, Irish physicist and mathematician George W. Named after the Stokes duo, it is a set of partial differential equations that express the conservation of momentum and mass as Newtonian fluids move.

The equation asserts that the rate of change (force) in the momentum of a fluid particle comes from changes in pressure acting on the liquid, dissipating viscosity forces, and gravity. Where viscosity is similar to friction, it arises from the interaction of molecules, and the more viscous the fluid, the stronger the effect.

The NS equation relies on differential equations to describe the motion of a fluid. Unlike algebraic equations, they do not seek to establish a relationship between the variables studied, such as velocity and pressure, but rather to establish a relationship between the rate of change or flux of these quantities. In mathematical terms, these rates of change correspond to the derivatives of the variables. Among them, in the simplest case of zero viscosity, the NS equation is reduced to Euler's equation, indicating that the acceleration (the derivative of velocity) is proportional to the derivative of the internal pressure.

This means that for a given physical problem, at least calculus can be used to solve the Navier-Stokes equation. Practically, only the simplest cases can be used to obtain a known solution in this way. These conditions usually involve non-turbulent flow in a steady state (the flow field does not change over time), where the viscosity coefficient of the fluid is large or its velocity is small (low Reynolds number).

For more complex cases, such as global meteorological systems such as el Niño or the lift of a wing, only a numerical solution to the Navier-Stokes equation can be obtained with the help of a computer. This field of science is known as computational fluid dynamics.

It is a chaotic model, and when there is a little inaccuracy in the input, the prediction results will be very different.

Incompressible fluids are usually modeled by the Navier-Stokes equations as above.

Because of its importance, "Navier-Stokes Presence and Smoothness" was listed by the Clay Institute for Mathematics in 2000 as one of the seven Millennium Grand Prix puzzles, with a problem solving prize of $1 million. Other problems juxtaposed with it include the Poincaré conjecture, the P/NP problem, the Hodge conjecture, the Riemann conjecture, the Young-Mills theory, the Beher and Sweeneton-Dell conjectures, and only the Poincaré conjecture has been resolved so far.

Back to this incident, the dean of the School of Mathematics at Peking University said in a media reply that someone had sent him to see the matter. He said: "Others can't do it, and it's very common for Wei Dongyi to be able to do it. First, Wei Dongyi is very smart. Second, he was very focused on doing mathematics. He just has a simple lifestyle, and we respect his wishes."

In addition, since the source only has a screenshot of the chat, the authenticity of this incident has also raised some doubts:

What do you think?

Reference Links:

https://weibo.com/1700040344/LrJRChoLk

https://www.zhihu.com/question/531599374