The Military-industrial Scientific Research System of the Academic Master Chapter 424

Chapter 424 I am the standard

 It wasn't until Chang Haonan stepped onto the podium and connected his laptop to the projector that the turmoil caused by him in the entire classroom gradually subsided.

The environment is even quieter than after Liu Hongbo came in.

 Because everyone is eagerly waiting to see what this textbook author, who is about the same age as themselves, can tell.

When writing this textbook, Chang Haonan included many basic mathematical concepts such as vectors, matrices, and tensors in the previous chapters because he considered the need for undergraduate teaching in the future, which is basically equivalent to The content of linear algebra is retold in general.

However, since it is a postgraduate course now, it is definitely not possible to start from this basic part, but directly to the basic concepts of engineering analysis and the introduction to the finite element method.

Of course, the first lesson, as usual, will not cover too much complicated content.

“I am very happy to be here and give you this first course on the principles and methods of numerical simulation.”

Chang Haonan did not start the intellectual content immediately, but made a slightly light-hearted joke:

“I remember when I was in high school, our math teacher often said to us, 'Do you talk or do I talk? How about you come up and talk?', I guess your middle school teachers also said similar things.”

 “But now, I seem to have really come up...”

 A cold joke that only students and teachers understood made the atmosphere in the whole classroom suddenly cheerful.

Even Liu Hongbo, who had sat next to the podium and took out a small notebook to take notes, also showed a knowing smile.

Although university teachers rarely care whether students attend classes, classroom discipline must still be maintained.

 Hence, he often used similar expressions.

 Unexpectedly, not only did a student come up to speak, but he also personally invited him to come up.

However, this paragraph will be the last tenderness that the entire classroom will experience in the next two and a half hours.

Chang Haonan did consider step-by-step when designing the structure of the textbook, but this does not mean that he will reduce the density of knowledge.

 In fact, even if a terrifying 288 class hours have been arranged, if Chang Haonan really wants to evaluate it, the progress of the course is still relatively tight...

"In a nutshell, the analysis of engineering systems requires us to idealize the system under study into a way that can be solved using mathematical means. In the not-so-complex practical problems that you may come into contact with during the postgraduate stage, we can Commonly used models are divided into two categories: lumped parameter models and continuum mechanics models, which correspond to what we often call discrete systems and continuous systems respectively..."

Chang Haonan quickly wrote on the blackboard while speaking.

PPT can indeed make teaching easier, but at least when Chang Haonan was a student, he still felt that writing on the blackboard could not be replaced to a large extent, at least for the classroom.

  Because the action of turning the pages of PPT is too simple for the lecturer on the stage, it is easy for people to ignore the students' receptive ability.

 The effect of the teacher writing the exact same content on the blackboard is generally better than just showing the PPT once.

As the chalk in Chang Haonan's hand gradually became shorter, the content on the blackboard became richer and richer.

“Before starting to solve a practical problem, the solution process can be divided into the following steps. The first is the idealization of the system, the second is the balance of the units, the third is the assembly of the units, and finally the corresponding calculations..."

“This idea is invariable in numerical simulation, especially in basic finite element method numerical simulation. Next, we will use a simple example and a complex example to demonstrate.”

“First, let's look at this steady-state problem… There are three rigid cars U1, U2, and U3 on the horizontal plane. Each car is connected through a linear spring system. Calculate the displacement of each car and the force in the spring under the following four load states...”

It is actually very easy to make simple things complicated in lectures so that everyone does not realize how serious they are. All you need to do is use jumping ideas and add all kinds of new concepts.

 But now Chang Haonan has long lost the motivation to show off his skills in front of these peers.

 The theoretical part of this course does require some talent, but at least 80% of the students in this classroom are from engineering majors.

After all, this is not an era where every undergraduate graduate will be able to do CFD simulations more than 20 years later.

From a practical point of view, most of them just need to be able to use this tool well, which is already very difficult.

For him, the most important thing is to introduce the content in a simple and in-depth way. It is best to allow everyone who takes this class to complete the basic introduction in two and a half hours, or at least realize the role of numerical simulation in engineering design. significance.

Therefore, although his pace is very fast from the beginning, for students who can go to Beijing Hang University for graduate school, as long as their minds keep following his writing on the blackboard, there will not be any insurmountable understanding gap.

 Soon, the first steady-state problem has been explained clearly.

 Following that, Chang Haonan turned the PPT to the next page and showed a smile:

“Next, let's try a slightly more complex problem.”

"This is a real practical problem, so if you can't understand it or can't follow the idea, that's normal. Don't be discouraged. This is just the first class. You just need to know that there is another way to face this kind of problem. A solution is enough.”

Chang Haonan's own projects are basically highly confidential, so it is difficult to teach them directly in class, so he directly "borrowed" a problem on the aeroelastic response and vibration load calculation of wind turbine blades from Fang Zhen.

Hearing what he said, the students who had just breathed a sigh of relief suddenly became nervous again.

“…The non-cyclic exponential function is expressed as Φ'(S)=4/M×exp(-S/Tα)=4/M×exp(-t/K1T1)…”

“Wherein the characteristic constant T1-c/a, a is the local sound speed, the factor K1=0.75/[(1-M)+πβ^2M^2(A1b1+A2b2)]…”    “…”

After all, it is from the steady-state problem of an almost ideal model to the graduation topic of Fang Zhen, a fourth-year doctoral student. It is still not difficult for these newcomers who have just entered their postgraduate career.

 In addition, Chang Haonan's statement just now that “it's okay if you can't keep up” did make some people less focused at this time than before.

“Here I go, I can still understand a little bit at the front, but the back feels almost like a book from heaven…”

The buddy who just chatted up Chang Haonan first had a pen in his hand and mumbled in a low voice with a blank look on his face.

　　"Okay, I felt like it was a book from heaven from the beginning..."

 Narrator Another person rolled his eyes at him.

“I can only say that he is worthy of being a textbook editor. It's so scary..."

 The third person also sighed.

“Have you noticed that Teacher Chang's book is still there, and I didn't take it with me at all…”

 Finally someone found a bright spot.

 The people around him almost all turned their heads to look at where Chang Haonan was sitting just now.

 Sure enough, a textbook was placed there.

In other words, those blackboard writings just now were all written by him without any reference materials...

"As expected of a textbook editor, it's so scary..."

 Another person also made the same exclamation.

However, among the majority of people who are confused, there are some great minds who can follow the whole process.

 Although I haven't learned many intellectual things yet, so the principles of some of the steps themselves may not be clear, but it is quite difficult to understand the overall process.

When Chang Haonan finally showed the calculated aerodynamic/elastic comprehensive motion equation, in addition to applause and exclamation, one person in the audience raised his hand.

“The student who raised his hand, do you have any questions?”

The person standing up was a rather thin boy wearing glasses that were almost half the size of his face:

“Before… uh, six pages of PPT, the part that calculates the dynamic stall model corrections.”

Chang Haonan was a little surprised that someone could ask such a detailed question at this point, so he quickly turned the PPT to the page the other person mentioned.

"Here you set the starting point of the analysis at the blade root, and set an equivalent angle of attack and an equivalent separation point. I don't understand why you do this..."

Chang Haonan turned around, glanced at the curtain, touched his chin and thought for a moment.

 There are several students below who have also understood a lot and have begun to guess.

“It should be to reduce the amount of calculation in the next step..."

“I think it's because it can make the equations written more symmetrical in form. I know many geniuses have this habit.”

 “Is this...”

Chang Haonan turned back and stood in front of the podium:

“Actually, there is no reason. Theoretically speaking, you don't have to set them at all. It's just that I randomly set two similar dimensionless quantities once before.”

Some people below have already breathed a sigh of relief, thinking that they have thought too much.

 But then Chang Haonan continued:

“Because it was actually the first project in the world to use this method to do aeroelastic modeling and analysis, so they all followed my method step by step and continued to do it, and now it has become a standard..."

 The whole place fell silent for a moment.

 (End of this chapter)

Chapter end