Chapter 40 Listen carefully!
Chang Haonan’s presentation at this group meeting was originally mainly for graduate students in his own research group.
Even Du Yishan's research team is not all 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 at all.
At most, you can just sigh and say how awesome it is afterwards, and you won't really learn anything.
That’s why he was going to start with 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.
Are these well-established professors tired of lengthy explanations of basic theories?
Would you like to show off your skills in simulation 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 made him finally decide to continue with the original plan.
“We know that the force exerted by a fluid on an object can be recorded as a function of 7 independent variables, F=f (l, θ, ρ, U, μ, ω, c), where l represents A certain representative length of the object, as the characteristic length of the study, θ represents..."
"After dimensional analysis, the force F on objects of the same type with similar geometry can be recorded as..."
"Let's discuss the dimensionless parameters appearing in the above formula in turn..."< br>
At the beginning, Chang Haonan was indeed a little nervous.
But as the explanation continued, he quickly got into the mood, and the chalk in his hand quickly wrote one equation after another on the blackboard.
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 understood at best.
After being reborn and receiving system buffs, these 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 1980s to the early 1990s was when the aviation industry was most impacted by new knowledge.
A large number of previously untouched theories and technologies 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 numerically solve the N-S equation. This method does not require approximate processing of turbulent flow, so its calculation results are more accurate, but in most cases, this This solution method requires too much calculation and is completely unrealistic based on current computer performance.”
“For indirect numerical simulation methods, there are two main branches, namely Reynolds average method and Large eddy simulation method..."
"The turbulent kinetic energy and dissipation rate equations of the RNGk-ω model of the Reynolds average method are very similar to the standard k-ω model. By integrating the previous equation 47, it can be accurate to The influence of effective Reynolds number (vortex scale) on turbulent transport, which helps to deal with the simulation of low Reynolds number and near-wall flow problems..."
Unconsciously, Chang Haonan has already put the four things in front of him into perspective. A huge blackboard is filled 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 in this part, so many people have already opened their notebooks and started taking notes.
Not to mention the graduate students who were brought here.
We are all people who continued their studies after graduating from undergraduate degree. 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 a very impatient tone:
"Don't move, listen carefully!"
< br>(End of this chapter)