Chapter 58 Project Progress
Lin Shikuan and others also graduated from prestigious schools, and their abilities are naturally not bad. Therefore, after Yao Mengna pointed out their problems, they almost immediately understood what should be done next. did it, and then immediately started a new round of work.
"By the way, please give me a copy of the previous aerodynamic modeling."
Chang Haonan looked at the few people who returned to the work station and were about to start working and said quickly, Afraid that it would be too late, they deleted the previous design files.
"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.”
Hear Chang Haonan’s explanation Afterwards, Lin Shikuan showed a happy 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 introduced by China from Italy is generally referred to as A-bomb internally. It is currently the One of the only two missiles of the Chinese Air Force that can attack beyond visual range.
"Well... we did not carry out the surveying and imitation work of the A bomb, so the three-dimensional modeling has not been done yet." Lin Shikuan thought for a while and then said: "But there was a way to transfer the paper drawings before A two-dimensional design drawing reserved for digitization. "
"That's okay, anyway, the aerodynamic modeling of the A bomb is very simple, I did it myself."
A few minutes later, Chang Hao. Nan held two floppy disks in his hands and sat in front of a computer by the window.
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 whole aircraft now?"
"There is no rush for the whole aircraft. That will take a while. I will do the wing part first."< br>
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 shapes of most aircraft are close to left-right symmetry, and the performance of computers these days is really bad, so you can take half of the model for analysis and leave the other side 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 the first time the two met. , the other party is also using CATIA to model a MiG-21.
But she didn’t know why, but she never saw Chang Haonan show that inhuman speed of operation 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 not be polite to come over to watch, and it seemed to be stealing. The teacher's suspicion.
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 shape surfaces will cause the edges to degenerate into points. This The form of a triangular patch is a fatal trap in digital shape design, which will lead to a situation where the normal vector is zero near the degeneration point."
"This is generally not a problem in the shape design stage. , the crisis broke out in the structural design stage, because of the emergence of zero normal vector, the structural parts could not be operated or even configured, which caused the entire related design process 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 that has neither line breaks nor comments, but must debug it.
Obviously, the mistake just mentioned hit the target directly. I am afraid this is how they dealt with this problem.
So after he said that the solution was to "stretch the vertices of the triangle into two points, and deform the triangular surface into a quadrilateral surface within the allowed tolerance range", four of the six people immediately He returned to his seat and began to make modifications, leaving only Lin Shikuan and one other person to stay in their original positions.
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.
"Speaking of which, Dr. Chang, you suddenly want to model the A bomb, shouldn't it be just to give us a few lectures?"
Seeing the modeling work of Chang Haonan at hand It was over, and the aerodynamic models of the two missiles were also 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 bombs?" Lin Shikuan was stunned for a moment:
"But the August 3rd Project has not yet started test flights with bombs."
"Digital design and aerodynamic simulation are originally It’s just to guide the design and test flight work, and of course it must be completed before the test flight.”
Yao Mengna, who had been silent just now, put her hand on her forehead with 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 delta wings, when this aircraft flies with bombs at supersonic speeds, the aerodynamic control surface, especially the aileron control efficiency, will be interfered by the airflow on the wing. It has dropped drastically, so I want to use simulation to verify it now to see how it can be improved."
"Huh?"
Lin Shikuan's expression was almost dumbfounded.
(⊙⊙)
(End of this chapter)