Chapter 40 Listen carefully!

Chang Haonan's presentation at this group meeting was originally mainly for graduate students in his own research group.

Even in Du Yishan's research team, not all of them are people like Yao Mengna or Fang Zhen. Most of them have a relatively poor foundation in this area.

If we start directly talking about the simulation calculation process, for these people, it is basically equivalent to just looking at the facts.

People often don't understand things that they don't understand at all.

At most, you can just sigh and say how awesome it is afterwards, and you won't really learn anything.

Therefore, he planned to start from the theoretical part at the beginning.

But just now when he saw many teachers sitting in the audience, Chang Haonan did feel shaken for a moment.

Will these well-established professors get bored of lengthy explanations of basic theories?

Do you want to show off your simulation skills first?

But the sentence Du Yishan just said mentioned two very crucial words:

Audit.

No matter how many people are sitting below, except for members of the same group, they are all listening.

This finally led him to decide to continue with his original plan.

"We know that the force of fluid acting on an object can be recorded as a function of 7 independent variables, F=f (l, θ, p, U, m, w, c), where l represents a certain representation of the object Length, as the characteristic length studied, θ represents..."

"After dimensional analysis, the force f exerted on geometrically similar objects of the same type can be recorded as..."

"Let's discuss the dimensionless parameters appearing in the above formula in turn..."

At the beginning, Chang Haonan was indeed a little nervous.

But as the explanation continued, he quickly entered the state, and quickly wrote one equation after another on the blackboard with the chalk in his hand.

Even people with relatively weak theoretical foundation can form a complete cognitive system for computational fluid dynamics simulation as long as they follow his ideas.

This is the power of knowledge given by the system.

In the last life, Chang Haonan was certainly very familiar with the application of computational fluid dynamics.

But when it comes to these theories, they can only be considered understanding at best.

After being reborn and receiving system buffs, this theoretical knowledge seemed to be engraved in his mind.

In the past, Chang Haonan actually felt that this basic theory was of little use, and it would not delay its application anyway.

But when the projects he was going to do later became more and more complex, he realized that this view was so wrong!

If you don't master the basic principles, you will always be following in the footsteps of others.

In fact, this cannot be said to be Chang Haonan's problem alone.

The period from the late 80s to the early 90s was when the aviation industry was most impacted by new knowledge.

A large number of theories and technologies that had not been exposed before poured into the country in a very short period of time, and they came from both the Soviet Union/Russia and the West.

Many times, the professors giving lectures on stage and the students listening in the audience are still in the learning process.

Therefore, except for some truly gifted and talented college students of his generation, what they learned was somewhat... extensive but not sophisticated.

That's why Chang Haonan chose such a more transparent way of speaking.

On the other side, Tang Lintian, who was listening below, had realized that there was something wrong with his judgment just now.

Although I haven’t talked about the specific application part yet, such a solid theoretical ability is definitely not something that a novice who needs to report learning progress in a group meeting can possess.

At this time, what Chang Haonan was talking about finally entered the numerical simulation part.

"The direct numerical simulation method is to directly solve and calculate the NS equation numerically. This method does not require approximate processing of turbulent flow, so its calculation results are more accurate. However, in most cases, this solution method is too computationally intensive. Huge and completely unrealistic given current computer capabilities.”

"For indirect numerical simulation methods, there are two main branches, namely the Reynolds average method and the large eddy simulation method..."

"The turbulent kinetic energy and dissipation rate equations of the RNG kw model of the Reynolds average method are very similar to the standard kw model. By integrating the previous equation 47, the impact of the effective Reynolds number (vortex scale) on turbulent transport can be accurately determined. This has Helps in the simulation of low Reynolds number and near-wall flow problems..."

Unconsciously, Chang Haonan had filled the four huge blackboards in front of him with writing.

Tang Lintian is deeply immersed in simulation, and he also knows all the things Chang Haonan talks about, so he can devote some energy to paying attention to the status of other people around him.

Compared with the basic physics content just now, even some teachers do not understand the theoretical part of simulation thoroughly, so many people have already opened their notebooks and started taking notes.

Not to mention the graduate students who were brought here.

They are all continuing their studies after graduating from undergraduate degrees. How could they not realize that the computer age has arrived?

However, after all, there are only a few people who can rely entirely on self-taught.

Most people just hang around in front of the door of this field and are not allowed to enter, or they reluctantly get in but don't get the point.

In this case, a systematic theoretical explanation almost from scratch is tantamount to a guiding light for these people.

At this time, almost an hour and a half had passed since Chang Haonan started his lecture, but most people in the classroom still maintained their rapt attention.

For Tang Lintian, this was even more surprising than the content itself.

As a professor who often teaches students, he knows very well where the limits of the classroom are.

A class lasts 45 minutes, and most people can only concentrate for 30-35 minutes. After that, even good students will be more or less distracted.

But in the current classroom, 90 minutes have passed, and this has not happened at all.

Tang Lintian also opened his notebook.

However, what he recorded was not the knowledge points taught by Chang Haonan, but a recollection of the latter's teaching methods from the beginning to the present.

About ten minutes later, looking at the contents of the notebook, he shook his head with some self-deprecation.

I didn't feel anything just listening to the lecture, but now after I listed the other person's ideas, I realized that being able to explain complex knowledge in a simple and profound way depends entirely on the other person's profound theoretical skills.

Even if he wanted to turn these things into lesson plans, it would take a lot of effort.

However, Chang Haonan stood in front of the podium and explained without writing!

Thinking of this, Tang Lintian suddenly became curious.

What kind of progress can a beginner make after listening to the entire explanation process just now?

Coincidentally, sitting next to him was a boy who looked like a student and was wearing a shirt. At this time, the latter had already taken notes on about the fifth page.

So while Chang Haonan was wiping the blackboard, Tang Lintian stretched out his pen and lightly touched the other person's arm, preparing to ask him how he felt after hearing this.

Unexpectedly, the boy didn't even raise his head, he just shook his arm and said in an extremely impatient tone:

"Don't move and listen carefully!"