Spark

On the other side, Chen Nian and Chen Guo rushed to the airport in a special car, without talking all the way.

In fact, at the level of two people, it was not enough to arrange a special plane, but there happened to be a plane that was about to go to Chang'an to perform a mission, so the two of them took a ride.

This flight will last for more than four hours. Chen Nian didn't want to waste time, so he took out the aerodynamics notebook he had prepared earlier on the plane and started to study.

It is said to be learning, but in fact it has progressed to this stage, mainly based on calculations, and the objects are also many difficult problems left over from Chen Guo's notebook.

Chen Guo, who was sitting on the side, looked at his hands curiously, and asked:

Isn't this my notebook? Have you read it all?

That's right. You said you can read what I saw on the desktop in your study, so I won't ask for it.

Chen Nian replied with a smile.

No, my point is, have you finished reading it all? How long has it been?

I've read it, but it's just a preliminary understanding. I don't even have an idea for more than half of the questions left in your notebook at the end. Those who have ideas don't know what method to use to solve them. Isn't this a proper research?

Hearing his words, Chen Guo nodded slightly.

In fact, his notebook is not left over from his college days, but after he graduated with a Ph. Learn again.

All that remains is this notebook.

Therefore, this notebook does not represent the knowledge level of a talented undergraduate student, but the review and organization of a doctoral student.

Naturally, his concerns will not be those of undergraduates.

Most of the dozen or so questions at the end of the notebook were the most cutting-edge topics at that time, including the problem of high angle of attack flow around, the problem of pulsating cross-wind, the measurement method of hypersonic boundary layer instability, and so on.

If these problems can be solved at Chen Nian's current level, then there are really ghosts

Thinking of this, he said:

You don't need to put too much energy into these questions for the time being, because every question I listed later is actually a complete research topic.

If you want to solve it, it will take a lot of time and manpower to complete it through a lot of experiments.

Now you still focus on laying the foundation. Read more about the exercises in the textbook. If necessary, I will find some other exercises for you to do.

Whenever I think your level is enough, I will pull you into the group and study with other graduate students.

Chen Nian nodded, he had already realized this situation, but...

Not all of the dozen or so problems must be solved through experiments!

For example, the aerodynamic uncertainty mechanism of high angle of attack, in fact, has obtained sufficient data when analyzing the F-22 airframe, and now he just lacks a simple method to organize it.

——

Or to put it more clearly, he already has the answer, but he doesn't know how to write it out.

Professor Chen, I understand what you said.

However, when I was looking at your notebook before, I also had some experiences and wanted to chat with you.

For example, the problem of aerodynamic uncertainty at high angles of attack, I feel that there is actually a way to solve it—especially when the slender body is used as a template for analysis.

You see, the essence of this problem is actually to solve the problem of asymmetric flow around slender aircraft—such as missiles and fighter jets, when maneuvering at a large angle.

Its difficulty lies in the fact that the flow and aerodynamic characteristics of the slender body aircraft are too complicated under the condition of transonic speed and high angle of attack.

However, no matter how complex it is, it can be broken down into several problems in the end.

The first one is the asymmetric separation of the front vortex when the angle of attack is above 30 degrees; the second is the lateral aerodynamic force reaching the normal force; the third is the randomness of the front vortex.

These problems lead us to solve the Navier-Stokes equation, the larger the angle of attack, the worse the linearity, and finally it becomes almost random.

But what if we find a complementary mechanism that can reduce the randomness of the Navier-Stokes equation? Or, what if we can reduce the probability of asymmetric vortex field generation through a certain shape design?

Chen Nian finished his deduction in one breath. In fact, he already knew the answer to this question.

The symmetrical + word layout will induce the generation of asymmetrical front vortex field, amplifying aerodynamic uncertainty. To solve this problem, the best solution is either a flat front wing layout, similar to a waverider, or an asymmetric front wing, similar to Certain surface-to-air missiles that can turn at right angles.

But how to deduce from the problem to the conclusion is a bit beyond his ability.

——

However, even if it was just like this, Chen Guo, who was listening on the sidelines, was so startled that his eyes almost popped out.

He actually thought of using the Navier-Stokes equation to solve the flow around a slender body?

No, he could actually explain the basic reason for the aerodynamic uncertainty at high angles of attack?

I didn't write this thing in my notebook!

You know, I have been specializing in the direction of high angle of attack mechanics in aerodynamics since my graduate school, and the aerodynamic uncertainty of high angle of attack is the most difficult part of it.

For a long time, the domestic aviation research field has not had a safe solution to this problem.

What was the solution then?

Don't fly high angle of attack!

Or, if it is necessary to fly with a high angle of attack and a large angle, it can be achieved by widening the wing surface.

This is clearly a compromise for stability.

It wasn't until the last few years that due to the increase in the timing of wind tunnel simulations and the more accurate simulation results of some problems, there has been a breakthrough in this problem.

And the solution

Do you know how to solve this problem?

Chen Guo asked.

Chen Nian hesitated for a few seconds before replying:

I haven't finished pushing, but based on the current direction, I can roughly guess the result.

I think the first thing to solve is the problem of the cross-symmetrical airfoil. The waverider can completely solve this problem, or use a spiral asymmetrical airfoil-of course, this is only for missiles.

For aircraft, it must be the F-22's multilateral wing auxiliary lift layout. We have also discussed this before. The wing surface vortex will offset part of the asymmetric separation of the front vortex.

boom!

The cup in Chen Guo's hand hit the small table heavily, and he looked at Chen Nian in disbelief, as if looking at a shining treasure.

After a long time, he asked intermittently:

This conclusion. Is it you who came up with it yourself?

Chen Nian nodded, and took out another notebook from his backpack.

And that notebook is densely packed with his own calculation process.

It's not considered to be launched, it can only be said to be half-determined and half-guessed. My current foundation is still too weak.

Are you still weak?

Chen Guo's eyes widened.

Your level is better than when I was in the second year of graduate school!