Chapter 303 Testing the Mathematical Model of ‘Plasma Turbulence’ (Second Update, Please Give Me a Monthly Ticket)
Xu Chuan didn't pay too much attention to the theft of his manuscript. After all, it was part of the plan.
That evening, Zheng Hai sent back the lost manuscript.
Although Xu Chuan was a little curious about which country had taken his manuscript from him, the security personnel were still dealing with the matter, so it was not easy for him to ask further questions.
As the days passed, the modeling work of plasma turbulence in controllable nuclear fusion reactors was carried out bit by bit.
In mid-September, about half a month later, the raw data of sterile neutrinos analyzed jointly by NTU and Jiaotong University was completed.
Chen Zhengping immediately called Xu Chuan and handed him the analyzed data.
"The analysis data has been sent to you, but the amount of analyzed data is still relatively large. After all, this is the special collision mathematics of the LHC. Do you need our help?" In the office, Chen Zhengping looked at Xu Chuan and asked.
The sooner the better for the discovery of sterile neutrinos, whether it is for Xuchuan or Nanda, or for the entire country of China. Because no matter from which aspect, the direction of sterile neutrinos has greatly enhanced the academic influence of individuals, schools, and countries in the academic world.
Xu Chuan thought for a while and said: "That's okay. In this way, I will compile a document on how to distinguish and confirm the confidence level of sterile neutrinos, and then you will process it according to the document, and the processed data will be handed over to me to prepare. How about Dariztu?”
Chen Zhengping nodded: "Absolutely. At present, the most important thing is to increase the confidence level of sterile neutrinos from 3 sigma to more than 5 sigma as soon as possible."
Xu Chuan smiled and said, "Then I'll trouble the teacher."
Compared to last year's Chinese New Year, he really couldn't spare much time to process the sterile neutrino data this time.
At present, it is more important for him to seize the time to complete the modeling of plasma turbulence, and it is indeed easier to leave the data analysis of sterile neutrinos to Nanda and Jiaotong University.
Chen Zhengping smiled and said: "You don't have to be so polite. In fact, we have to thank you for giving us this opportunity. After all, for other students, this is rare experimental data."
For NTU and Jiaotong University, it is also a good thing to allow physics students who have not had the opportunity to participate in CERN experimental data analysis to participate in some high-energy physics data analysis work.
After all, not every student studying theoretical physics has the opportunity to follow a mentor or apply for an internship at CERN.
More theoretical physics students often gain some experimental experience at home or elsewhere to complete their graduation thesis.
This time, the analysis data of optically inert neutrinos is enough for a large number of physics students from Nanjing University and Jiaotong University to complete their graduation thesis. You might even be able to take this opportunity to get the qualifications to set foot at CERN.
As Nanda and Jiaotong University began to analyze the experimental data of sterile neutrinos in depth, Xu Chuan's mathematical modeling work on plasma turbulence is gradually coming to an end.
Establishing a mathematical model for plasma turbulence is difficult even if we put aside the underlying complex mathematical calculations and related theoretical foundations.
During the modeling process, Xu Chuan encountered a lot of troubles.
Some things can be solved through various searches and learning, but some questions simply cannot be answered on the Internet.
For example, he encountered difficulties when implanting "eddy current direct simulation data" into the model.
Because there are differences between the large and small scales of eddies, and both must be solved at the same time, it will be very expensive to solve all turbulence scales in numerical simulations.
Especially when used to solve high Reynolds number flows, even with a supercomputer, the calculation may not be completed in a short time.
If it's in other fields, it doesn't matter.
But for real-time control of high-temperature plasma turbulence in controllable nuclear fusion reactors, timeliness is of vital importance.
Without real-time control, it will be too late to wait until the plasma hits the first wall.
Looking at the crude model and the half-written modeling program on the screen, Xu Chuan let out the turbid air in his chest.
To be honest, he has been troubled by this problem for a long time. Before, he could skip it and do other work first, but now he has to make up for it.
"Perhaps, I need some foreign help." Staring at the slowly rotating model on the screen, Xu Chuan shook his head slightly.
Strictly speaking, he has not comprehensively and systematically studied mathematical modeling. He can write some simple models, but it is almost impossible to solve this problem based on his own ability.
Of course, it is normal to ask for help when encountering problems during research, and there is no shame in it.
I'm just saying, who is better to ask for help?
After thinking about it, a figure appeared in Xu Chuan's mind. After confirming it, he opened his mailbox, sorted out the problems he encountered, the required conditions, and some relevant theoretical data and foundation, and sent it.
Then he picked up his phone again, opened Weixin, found a familiar number, and sent a message.
After a while, the phone vibrated, and a prestige reply came over.
"Well, I received the email you sent. I'll take a look at it first, but I may not be able to solve it."
Xu Chuan smiled and replied: "Thank you for your hard work. I will treat you to dinner when you come back."
For work on mathematical modeling, the first thing he could think of was his senior sister Liu Jiaxin.
In 2018, he returned to China, and the senior went to Princeton for further studies. Now more than a year has passed.
With her mathematical talent and learning ability, she should be able to learn a lot in Princeton, and maybe she can help him solve this problem.
Putting down the phone, Xu Chuan put his attention back on modeling. Although he asked someone to help him, he had to study it again.
After all, knowledge is something that is never afraid of too much, but only afraid of not having enough when it is used.
The senior's reply came much earlier than Xu Chuan expected. In the evening, an email asking him to keep an eye on it came back.
At the same time, he also received a message from the senior on his WeChat: "Well, the plan has been sent to your email. Please see if it is suitable. If not, you can tell me again."
When Xu Chuan received the WeChat, he was eating. After replying a good message, he cleaned the food on the plate in a few bites and rushed back to the office.
When he opened the mailbox, there was indeed an unread email in it.
Clicking on the email, Xu Chuan quickly browsed it.
".According to the requirements, if you need to simulate the 'direct numerical value of eddy currents', you cannot achieve the required effect whether you use DNS simulation, LES splitting method, or Reynolds average simulation RANS method."
"Because the characteristic Reynolds number in plasma turbulence engineering problems is generally high, even the maximum scale in the attached boundary layer will become very small, and even if the LES model is used, the requirements for the grid scale are not much weaker than DNS."
"This is the core basic problem."
"And if you want to reduce the requirements for computer hardware and computing power, maybe you can try to use the edge An anisotropic model, such as the RANS model, is used near the boundary layer, while the LES model is used in the area far from the wall. A framework of a revived high-order model is completed through double hybridization."
"Let the Reynolds stress term τ=ρR^ij"$^$" represent the Favre average, and the six-component equation has the following general form:
[ρR^ij/t+(ρu^kR^ij)/xk=ρPij+ρΠij+ρεij]
"The right-hand side is the generation term, the redistribution term of the pressure and strain correlation term, the dissipation term, the diffusion term and the mass term, respectively. The generation term can accurately obtain the required function."
"By introducing the transition function F, the RANS method is applied near the boundary layer, while the LES method is used in the area far from the boundary layer, and the second-order moment model under the hybrid RANS/LES framework can be constructed:"
[R^hybridij=FR^ij+(1F)R^sgsij. 】
"Perhaps such a high-order moment model has the potential to accurately distinguish eddy flow, which meets your requirements."
"I hope it can help you a little. ”
In front of the computer, Xu Chuan carefully read the solution sent by Liu Jiaxin.
Perhaps it was the experience of studying abroad for more than a year that affected some of her personality, or it was across the computer screen, or it was just in her own professional field, the confidence shown between the lines of the email by this senior sister was much higher than before.
Of course, it must be said that the solution proposed in this email may really solve his problem!
Not only is it detailed, but it also lists all the key nodes in modeling.
And being able to make such a detailed plan in just a few hours, it can be imagined that it is not only that she has a very deep understanding and high ability in modeling.
It is more likely that after receiving his email, she has been working hard to solve this problem, otherwise it would be impossible to make such a plan in a few hours, with detailed nodes attached.
After reading the email, Xu Chuan Lianshan quickly replied with a smile: "I have received it, I will try it first, whether it succeeds or fails, I will tell you. "
"I have a hunch that it can help me solve this trouble. Thank you for your hard work. ”
After downloading the solution from the mailbox, Xu Chuan reopened the FloEFD modeling tool. After backing up the original model, he began to modify and rewrite the mathematical model according to the ideas of the senior sister.
This time, the modeling process was quite smooth.
When he typed the last line of formula on the computer and carefully saved the finished model, he relaxed.
After a long breath, Xu Chuan put down the ballpoint pen on his fingertips, looked at the mathematical model on the display, and smiled.
"Finally done! "
After stretching and stretching his muscles, Xu Chuan checked the mathematical model he had made, and after confirming that there was no problem, he copied it down.
He left the office with the solid-state drive containing the model.
The mathematical model has been completed, so the next step is to conduct a simulation test on it.
This requires the use of a supercomputer. To run this model, even if it is just to calculate and deduce the phenomenological data, the computing power required is far beyond what the human brain can achieve.
Unless his brain is a sixteen-core quantum computer, otherwise this is simply impossible.
As a top 985 university, Nanjing University naturally has its own supercomputer.
The High Performance Computing Center of Nanjing University uses IBM's large blade cluster, with a theoretical computing peak of 873.6 trillion times per second, providing computing services for Nanjing University's physics, chemistry, atmosphere, astronomy, materials, electronics and other departments.
Although its performance is not excellent now, it is still possible to test the mathematical model in his hand.
Of course, Xu Chuan is not sure whether the supercomputer at Nanjing University can run his model, because the calculation involving turbulence has always been the most complex and computationally demanding of all calculations.
Even if he has made the model as simple as possible, the test for the supercomputer is estimated to be quite large.
The theoretical calculation peak is 34 trillion times/second. This computing power is not much for a phenomenological turbulence simulation control mathematical model, and it can even be said to be pitifully small.
Perhaps he should go directly to a national large-scale supercomputer center to do this test, but in comparison, it would be much more troublesome, and he might even have to wait in line.
It is different here at Nanjing University. As long as he needs it, it is just a matter of words to stop all other calculations and serve him, so he plans to try it at Nanjing University first.
Try it first, anyway, it won't get pregnant.
With the model, Xu Chuan found the teacher in charge of the supercomputing center in the administrative center. After filling out an application form for the use of the supercomputer, the teacher in charge of approval stamped the application form with a red seal.
As long as this person's application form is not intended to play games with the supercomputer, it will be approved 100%.
What's more, the teacher in charge of stamping also glanced at the content of the application.
"Testing the mathematical model of plasma turbulence."
Although he is not a professional, this teacher in charge of administration knows the name of plasma turbulence, which is a world-famous problem.
In this case, he passed it without even reporting to the leader.
For fear of delaying this person's research.
After all, a report can be made up later, but if it delays this big guy's business, it is estimated that the principal will hang him at the school gate and beat him.