Chapter 11 Senior Sister Suspicious of Life [Seeking for further reading]
At this time in the first half of 1996, even the security in the capital was not very good, so a few people did not eat too late, before eight o'clock Zhong left the hotel, Wu Yifan went to the house he rented outside the school, and the other three naturally went back to school together.
In the college dormitories in the 1990s, entertainment activities were far less abundant.
Chang Haonan remembers that there were a few roommates in his dormitory who particularly liked playing cards. Except for a period of time before the exam, they basically had to play hard every night.
So he did not choose to go back to the dormitory directly. Instead, he went to the public phone booth and called home.
The moment he heard his parents' voices when they were young again, Chang Haonan almost cried.
In order to prevent the second elder from hearing anything unusual, he hung up the phone before chatting for too long, saying that he was going back to the dormitory to rest.
It took almost ten minutes for Chang Haonan to finally calm down and then decided to go to the library again.
This time it is not for course design, but there are several newspaper racks in the rest area of the library, which will provide the latest newspapers and magazines.
Having just been reborn, he has basically no memory of recent events, and there is no developed Internet in this era, so that is the most convenient place to get news.
A few minutes later, Chang Haonan moved a stack of newspapers and sat on the bench next to him.
When reading the news, he only needs to know a general idea of the matter, so that not knowing anything seems very strange. Therefore, he highlights the news and reads it very quickly.
The aftermath of the incident at the beginning of the year is still lingering, and many news reports are still related to it. Some military publications are comparing the military power between China and the United States. In this era, there is no need to say more about the results.
Multiple shootings occurred last month.
The last module of Mir, the Nature module, was launched into orbit and successfully docked, completing all construction work of the space station.
...
They are all very contemporary content.
Just when Chang Haonan saw the crash of Valuje Air Flight 592, a familiar voice suddenly came from behind him.
"Junior Chang? You look very relaxed today?"
He turned around and found that it was the senior Yao Mengna whom he met in the computer room that day.
"It's about combining work and rest. Students in our new era have to read books about sages and see things outside the window." Chang Haonan looked up at his watch and found that it was almost 10:30 pm when the library closed, so he stood up and turned around. He put the books and newspapers back into their places one by one, then put on his bag and left the library with Yao Mengna.
The total distance from the newspaper area to the library entrance was less than 20 meters, and Yao Mengna secretly glanced at Chang Haonan no less than five times.
She came here today to find some information about CFD simulation. A project being carried out by the research team was not going well. She and two other people tried for a long time but failed to find an efficient calculation method.
So when she saw Chang Haonan just now, Yao Mengna almost subconsciously walked over and said hello.
Subconsciously, she thought that this junior undergraduate student might be able to solve this problem.
But when the question came to her lips, Yao Mengna still hesitated.
Firstly, the problem this time was much more complicated than the previous simulation Chang Haonan conducted in the computer room. Secondly... Chang Haonan really caused her huge psychological trauma last time.
But in the end, she decided to put aside her face issues for the sake of the research group's project.
"Brother, can I ask you a question related to computational fluid dynamics?"
After hearing this question, Chang Haonan's first reaction was disappointment.
He originally thought that Yao Mengna noticed his handsome appearance and kept peeking over here, but it turned out that the other party was attracted by his inner wisdom.
Why can't it be more superficial?
However, he nodded calmly: "Okay, let's talk."
"I am studying an aeroelastic instability problem that considers large geometric deformation factors for the aircraft wing. But the efficiency of solving the N-S equation and the Euler equation using similar ideas to yours that day is very low, and we have tried several results, and the errors are relatively large..." "Wait a minute." After hearing this, Chang Haonan raised his voice directly. He interrupted Yao Mengna's question: "What kind of wings are they?"
"Uh..." Yao Mengna was stunned: "I just want to ask about the simulation idea, does this have a big impact?"
"There is a huge difference between delta wing, swept wing and high aspect ratio straight wing. "Chang Haonan replied expressionlessly: "Of course your research group may have confidential projects, if it is inconvenient to tell me..."
"There is nothing inconvenient about making the project public!" From what Chang Haonan meant, it was obvious that he knew something about this aspect, and he immediately didn't care whether he was a junior or not.
“It is a straight wing with a large aspect ratio. We have also tried to improve the Dewey-Hodges equation, but the results are not ideal.”
“That is normal.” Chang Haonan shrugged, as if it were a matter of course: "The aeroelastic instability problem of a large aspect ratio straight wing is most likely a flutter problem. The computational fluid dynamics (CFD)/computational structural mechanics (CSD) coupling method does not Not applicable to this aspect of analysis.”
Wing flutter has been a fatal problem almost since the birth of aircraft.
It is a self-excited vibration formed by the interaction of aerodynamic force, elastic restoring force and inertial force of the structure.
In other words, once flutter occurs, it is a self-continuous movement that does not require the action of external forces, and the vibration amplitude will become more and more severe, usually causing irreversible damage to the aircraft within a few cycles. Structural damage.
This problem is especially obvious on large aspect ratio wings.
"This..." Yao Mengna opened her red lips slightly and looked at Chang Haonan beside her. She thought about countless possibilities, but she never expected that she would go in the wrong direction from the beginning.
And such a mistake was pointed out by an undergraduate almost without thinking.
Her entire worldview was almost shaken.
For a moment, Yao Mengna even began to doubt whether she had ever attended this university.
Chang Haonan quickly spoke again:
“The large aspect ratio wing can be regarded as a beam wing in structure, so the unsteady aerodynamic force can be passed through the coupling based on subsonic speed. The polar grid method is used for calculation. According to the linearization theory, one of the basic solutions to the unsteady linear small perturbation velocity potential equation is the acceleration potential dipole. Therefore, for the wing doing simple harmonic vibration in the airflow, the wing can be calculated. An acceleration potential dipole Δp/p is distributed above. At this time, the normal velocity amplitude on the wing must meet the corresponding vibration boundary conditions, so that Δp can be solved. Of course, this method is only suitable for linear problems.”
Chang Haonan, who noticed Yao Mengna stopped, also stopped and looked back at the other party: "Do you understand?"
This tone again...
Yao Mengna's breathing suddenly became heavy. .
The fists are hard.
But...
If you are not as skilled as others, you will be at a disadvantage.
She finally chose to reconcile with herself.
“I understand, since we have to use the dipole grid method, wouldn’t it be better to use the MSC.NASTRAN software?”
Yao Mengna was able to deeply participate in the project in her second year of Ph.D. The big project of the group is naturally no ordinary person. I just got a head start before. Besides, the dipole grid method is not a new theory. Now that I was awakened, I quickly understood what Chang Haonan meant.
She felt that she should have found a way.
"It seems that my college experience was not in vain..." Yao Mengna comforted herself in her heart.
However, Chang Haonan's next sentence poured cold water on her newly ignited hope: "The default MSC.NASTRAN should not be easy to use. If you really want to do well, I'm afraid You need to use the DAMP language rules to modify the solution sequence provided within the software for secondary development, but if you can’t see the actual problem, I probably can’t tell you anything more specific.”
“ ..."
Yao Mengna looked up at the bright moon in the sky. Although it was already late May, she felt that her mood could be described in one lyric.
Snowflakes are falling and the north wind is blowing
The world is vast~~~
(End of this chapter)