Chapter 2 Computational Fluid Dynamics Simulation

In 1996, it was an era when you had to wear shoe covers when entering the computer room. Computers were a new thing. Of course, students’ personal computers were almost non-existent. Even the school’s computer room could not be used unless approved by the college or a higher level. You can only use your student ID card for up to one hour a day.

At this time, Chang Haonan was sitting in front of a computer of unknown brand, looking at the familiar yet unfamiliar pictures on the monitor.

The classic fluid dynamics calculation software Fluent is a relatively new version compared to 1996.

The oldest fluent is just a partial differential equation solver and does not even have a meshing function. In that case, the workload will be several times greater.

Although Chang Haonan can perform smooth operations with system buffs, the computer itself in 1996 was really unable to respond smoothly, and what he lacked most at the moment was time.

But even so, the 3D modeling process still requires additional software, such as Dassault's CATIA.

"Now Ye Qing is really back, in a double sense."

Chang Haonan thought to himself as he looked at the CRT monitor, trackball mouse and win95 interface in front of him.

"Haonan, when did you learn these things?" Wu Yifan, standing behind Chang Haonan, had curiosity in his eyes.

Of course what he was concerned about was not Chang Haonan's ongoing simulation modeling work itself, but the latter's extremely skilled use of computers. He knew a big boss from Huaxia Renmin University. He made more than 200,000 yuan through computer programming when he was a sophomore, and he became his idol for a time.

"Of course when you go to contact business outside the school." Chang Haonan said without looking back.

Zhang Man and Zhou Shuwan, who were also standing behind Chang Haonan, had their jaws almost dropped with disbelief on their faces.

Compared to Wu Yifan, who was hardly interested in his studies, the two of them knew how difficult it was to model a complex structure like an aircraft, even if they just transferred the things they had already drawn on the drawings to the computer. It’s an astronomical workload for a novice.

However, all this was so easy in Chang Haonan's hands. As his fingers flew around on the keyboard and mouse, a fighter model with a large delta wing and a conventional layout gradually appeared on the computer screen.

Equivalent wing model, completed

Full machine pneumatic model, completed

Midway, the computer room management teacher came over to remind them that the time was up. Wu Yifan, who was afraid that Chang Haonan would be disturbed, decisively added an hour of his own time to the computer. Later, Zhou Shuwan and Zhang Man also contributed their student ID cards.

Inlet duct modeling…

Engine modeling…

"call……"

Under the "guidance" of the system, Chang Haonan almost entered a selfless working state. When he finally completed the required modeling work, he realized that several hours had passed.

"Is this... the end?" Zhang Man looked at the screen in front of him in stunned silence. Although he had just watched the entire modeling process, it still took him four hours to create a three-dimensional model with such high precision. She had a sense of unreality.

"Strictly speaking, of course not." Chang Haonan stretched out and leaned back on the chair: "But our course only requires aerodynamic design, so we don't care about airborne equipment, internal structures, etc. Anyway, we know that this plane can definitely fly."

"Awesome, Brother Nan, I think even among the professors in our college, there are not many who are more skilled than you, right?" Zhang Man did not hesitate to praise Chang Haonan at all, and his name has also changed. .

I originally thought that the big boss in the group was Zhou Shuwan, but it turned out that Chang Haonan, who seemed a little crazy before, was the real hidden boss!

No, study god!

How can the madness of Xue Shen be called madness? That’s just ordinary people not understanding God’s thoughts.

"If we only talk about simulation, it's pretty much the same."

Chang Haonan reached out and touched his thick hair, leaned back on the chair, and showed a confident smile. He is not just boasting. There may not be anyone in the world who is more skilled than him in this regard.

"But what we were talking about before was to calculate the performance of this aircraft?" Wu Yifan scratched his head. Although he also saw that Chang Haonan was powerful, he really didn't want to increase his own strength.

"Of course, but the calculation process will be more time-consuming, so this time I only calculated the performance of the inlet part. Next, I only need to use the finite volume method to solve the Euler equation for the flow field outside the body, and use the finite volume method for the flow field inside the inlet. By solving the NS equation, you can obtain more typical intake duct performance data."

Chang Haonan saved the model file and opened fluent to prepare for the next step.

For grid generation of complex shapes, partitioned structured grids or overall unstructured grids can be used. The partitioned structured grids have high computational efficiency, but the degree of automation of grid generation is low, while the characteristics of unstructured grids are opposite.

As a "scientific research tutor", the system naturally taught Chang Haonan all these two technologies, but the latter needed to choose one of them to output to the computer in front of him.

Although the new version of the software in 96 can already divide the grid, the function is not very complete. Considering that the performance of computers in this era is still slightly different from that of more than years later, Chang Haonan finally chose a computer with higher computational efficiency. former.

"Unit No. 27, it's time for you guys to board the computer again. This time..." At this critical moment, the computer room teacher's voice came from the door again, and this time they no longer had another student ID card to use. .

"Use mine."

A cold female voice sounded from the row behind Chang Haonan. Several people turned around and saw a tall girl with long hair shawl, wearing a light blue dress and round glasses stood up and handed over a certificate with a red cover. He handed it to the computer room teacher: "I got off the plane here, and it's theirs after that."

That certificate was obviously unusual. The computer room teacher just glanced at it and turned around and walked out of the computer room without even writing anything down in the notebook in his hand.

"Thanks……"

After all, he was a big help, so after the computer room teacher left, Chang Haonan quickly expressed his thanks, but after he spoke, he was not sure whether the other person was a teacher or a student.

"Yao Mengna, a second-year Ph.D. student, should be considered your senior."

While Yao Mengna made a brief self-introduction, she left the computer she had just used and came to the side of Chang Haonan and the others: "As long as you don't get off the computer, you can keep using this computer. You don't have to worry about anyone disturbing you anymore."

"Thank you so much, senior sister, we..."

Wu Yifan thanked him with a smile on his face, but he was interrupted in the middle of his words: "It's okay, I just want to see how you plan to continue. Are you going to conduct a fluid dynamics simulation on the entire machine?"

Obviously Yao Mengna was also interested in the modeling that Chang Haonan was doing, but because the four people spoke in very low voices just now, she could not hear the specific content clearly.

Chang Haonan nodded: "Yes, I am going to use Fluent to numerically solve the fully viscous Nevi-Stokes equation."

Yao Mengna's eyes widened slightly after hearing this answer.

She really hadn't thought about these people, or that this one who looked like an undergraduate was going to play so big - she had noticed these people in the row in front of her just now, and naturally knew that all the work was done by sitting at the computer. The person in front completed it.

In fact, even Yao Mengna, who is in the second year of her Ph.D., has only just begun to gradually come into contact with computational fluid dynamics (CFD) simulations of aircraft.

"You don't mind if I watch from the side, right?" Although Yao Mengna used a questioning tone, she sat on a chair next to Chang Haonan before Chang Haonan could answer: "Maybe I can still be of some help."

Although she said that, Yao Mengna herself didn't actually have a particularly clear idea. She mainly wanted to find some inspiration through Chang Haonan's approach. At this time, digital design and computer simulation are still new things to aviation designers across China.

While the two were talking, Chang Haonan had imported the just-completed modeling into Fluent and started meshing the finite volume method.

"Ah……"

Then came his moment to perform.

Fluent in this era does not yet have a beautiful graphical interface and a large number of preset models that can be directly called. Especially for complex simulations such as supersonic fluid dynamics, it can only complete part of it.

But this does not stump Chang Haonan, who already knows all the next steps.

Since the existing software can only complete part of the work, use Fortran language to write an algorithm for numerical solutions to partial differential equations.

Then call external programs to operate Fluent to complete the lazy part, and then use scripts to realize automated operations.

Yao Mengna, who was watching from the side, had a relatively relaxed attitude at first, but after just closing her eyes and yawning, she realized that she could no longer keep up with her thoughts.

In particular, Chang Haonan's code input speed almost took off, leaving her with no time to clearly see the function of each piece of code, let alone write down the entire process.

"that……"

Yao Mengna spoke hesitantly, wanting to ask Chang Haonan about his specific numerical simulation ideas, but for a moment she couldn't bear to ask the undergraduate question directly, so she had to use a more euphemistic way of saying it.

"Can we agree on our thinking? My ideas seem a little different from yours?"

"Okay, tell me your thoughts first, and I'll see if there are any problems."

Chang Haonan was completely immersed in work again, and he had only been reborn for a few hours, so he subconsciously thought that he was still leading interns in the research institute.

"what?"

Yao Mengna almost broke her guard with one sentence.

No, why do you want to see if there is any problem?

Do you really think of yourself as the standard answer?

Are you so confident?

And most importantly...

She couldn't think of a complete idea at all!

Yao Mengna took several deep breaths in succession and patted her chest again before she could catch her breath.

"No... no need, just tell me what you think and I will compare it myself."