The military-industrial scientific research system of the academic master.

Lin Shikuan and several others also graduated from prestigious schools, and their abilities are naturally quite good. Therefore, after Yao Mengna pointed out their problems, they almost immediately understood what to do next, and then immediately started working on a new round of work. .

"By the way, please give me a copy of your previous aerodynamic modeling."

Chang Haonan looked at the few people who were back at their work stations and said quickly, fearing that they would delete the previous design files if they were slower.

"Before? But didn't you just say..."

Lin Shikuan turned back to look at Chang Haonan in confusion.

"It is really troublesome to modify the design, but I am going to do a fluid dynamics analysis on the original design, so as long as the accuracy of your model is high enough, it will be fine."

After hearing Chang Haonan's explanation, Lin Shikuan showed a relieved smile on his face.

That was Party B’s expression when he discovered that the scrapped case he had done before could still be used as waste.

"That's definitely no problem. We can still guarantee this."

"Also, Team Leader Lin, do you have any modeling of the aerodynamic shape of the A-bomb?"

The Aspaid air-to-air missile imported by China from Italy is generally referred to as the A bomb internally. It is currently one of the only two missiles of the Chinese Air Force that can attack beyond visual range.

"Well... we are not doing the mapping and imitation work of the A-bomb, so the three-dimensional modeling has not been done yet." Lin Shikuan thought for a moment and then said: "But there are two aspects that were retained when the paper drawings were converted to digital. dimensional design drawings.”

"That's fine too. Anyway, the aerodynamic modeling of the A bomb is very simple. I did it myself."

A few minutes later, Chang Haonan sat in front of a computer by the window with two floppy disks in his hands.

The digital design team was not taken seriously due to the delay in producing results. There were only five people in the team including Lin Shikuan himself, so there were many empty seats in the computer room.

Yao Mengna also took the opportunity to sit in another seat closest to him.

"Are you ready to start aerodynamic analysis of the entire machine?"

"It's not urgent to complete the whole machine. It will take a while. I'll do the wing part first."

Chang Haonan said that he had already opened CATIA and began to process the model before analysis.

As he worked quickly with his hands, the three missile pylons that had been modeled before were gradually "installed" under the left wing.

The aerodynamic shape of most aircraft is close to left-right symmetry, and the performance of computers these days is really bad, so half of the model can be taken for analysis, and the other side is left alone.

"I think... you should use the A bomb as an example to demonstrate to them."

Yao Mengna looked at Chang Haonan's movements and couldn't help but recall that when the two met for the first time, the other party was also using CATIA to model a MiG-21.

But she didn't know why, but she never saw Chang Haonan show such inhuman operating speed again.

"Yeah... that's okay."

As soon as he finished speaking, several people from the digital design team quickly moved chairs and sat around Chang Haonan. Even Yao Mengna, who made the suggestion in the first place, barely reacted.

In fact, someone just noticed Chang Haonan's extraordinary work efficiency, but they were worried that the latter was not an employee of the 601 Institute. It would be impolite to come over to watch, and it seemed to be stealing from his teacher.

Now that I have the consent of the owner, there is no need to worry.

"Before we parameterize discrete data, we must first consider the fitting problem of discrete data. The fitting problem can be divided into two methods: interpolation and approximation..."

Because Aspad is an air-to-air missile designed by Italians, its surface is originally expressed in the form of parametric polynomials. The modeling process is not complicated, so Chang Haonan focused on how to use parametric polynomials to construct curves or surfaces.

In fact, some excellent data parameterization methods are themselves secrets kept secret by major European and American aircraft manufacturers. Chang Haonan can only introduce some principles and techniques based on his own understanding and the experience of later generations.

"..."

"Since the expression of surface patches in software generally adopts the form of four-sided patches, the expression of triangular surface surfaces will cause the edges to degenerate into points. This form of triangular surface patches is a fatal problem in digital appearance design. Trap, which results in a situation where the normal vector is zero near the degenerate point."

"This is generally not a problem in the appearance design stage. The crisis broke out in the structural design stage. It was because of the emergence of zero normal vector that the structural parts could not be operated or even configured. As a result, the entire related design process needed to be completely overturned."

When Chang Haonan talked about how to deal with the large number of triangular surfaces in aircraft design, he heard a loud gasping sound like surround sound coming from behind him.

The feeling is similar to when a programmer faces a mountain of code that he wrote ten years ago without line breaks or comments, but must debug it.

Obviously, the mistake just mentioned hit the target directly. I'm afraid this is how they dealt with this problem.

Therefore, after he said that the solution was to "spread the vertices of the triangle into two points, and deform the triangular surface into a quadrangular surface within the allowable tolerance range," four of the six people immediately returned to their seats. The modifications began, leaving only Lin Shikuan and one other person to stay in place.

In fact, when Chang Haonan later participated in the appearance design of the JH-7A, he was fooled by the same mistake, and it took several months to completely rework it.

That's why he still remembers it.

Fortunately, Lin Shikuan and his team's previous progress was not fast, and the amount of tasks that needed to be changed was acceptable.

"By the way, Dr. Chang, you suddenly want to model the A-bomb. Isn't it just to give us a few lectures?"

Seeing that Chang Haonan's modeling work was finished and the aerodynamic models of the two missiles were hung on the hangers under the wings, Lin Shikuan scratched his head and asked.

"Of course not. In fact, I am planning to use the CFD/CSD coupling method to analyze the aileron control performance, wing load distribution and structural elastic deformation of the aircraft under bomb conditions."

"With ammunition?" Lin Shikuan was stunned for a moment:

"But Project 83 hasn't started test flights with bombs yet."

"Digital design and aerodynamic simulation are originally intended to guide the design and test flight work, and of course they must be completed before the test flight."

Yao Mengna, who had been silent just now, held her forehead with one hand and showed a helpless expression.

"This……"

Lin Shikuan certainly understands this truth, but the reality is that their digital design team has been catching up with the project progress since its establishment, and over time it has almost formed a thinking inertia.

"Not only that, according to my previous research on the aerodynamic characteristics of the delta wing, when this aircraft flies with bombs at supersonic speeds, the aerodynamic control surface, especially the aileron control efficiency, will be drastically reduced due to the interference of the wing surface airflow, so I Now we need to use simulation to verify it and see how it can be improved.”

"what?"

Lin Shikuan's expression was almost dumbfounded.

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