Back in 1978, I was admitted to Northwestern Polytechnical University.

Chapter 89, 288 chapters, all 288 chapters!

Northwestern Polytechnical University, computer room.

"By hand calculations, we can only divide the aircraft into a few simple finite element models. With computers, we can decompose it into much finer parts. Now, our project requires calculations of a fine mesh model with a scale of tens of thousands. The results obtained in this way are 100% reliable for static testing!"

"Tens of thousands, that's amazing! Qin Liang, just give us the task, we'll do whatever you say!" The students of Class 5381 were full of excitement.

The final exams were over, and the results were in. Although they felt the results were not ideal, the school was very satisfied and valued them highly. After the final exams, the school continued to provide them with dormitories and meal tickets, and allowed them to continue their research with the senior professors.

"Well, we don't have any tasks at the moment. The design plan from Institute 611 is still under review. Let's recalculate the Super 7 project. Their requirement is no more than 5% error, and we need to achieve less than 1% error ourselves!"

The static load that each part of an aircraft can withstand is a crucial factor. If it doesn't meet the standard, the aircraft may disintegrate during flight. If it is overly reinforced, it will result in an excessively heavy aircraft.

When developing an aircraft, the first aircraft is destined to take to the skies and enjoy immense glory. The second aircraft, however, will never be able to take to the skies. From the moment it is born, it will be sent to a static testing device to undergo various pressure tests.

If there is a design flaw, the device may disintegrate before reaching its rated overload!
If the design is sound, then after all the experiments are completed, we will continue to apply even greater stress to see how much it can exceed the design specifications. The final result will still be disintegration!
All of these are related to design, and how to design is of utmost importance!
The shape of an airplane is unique, with each part being different, making it impossible to describe it using a single partial differential equation. Even if it were possible, these partial differential equations would not necessarily have a unique solution.

What should we do in this situation?
This requires dividing the aircraft into countless interacting units and then solving it using mathematical approximations, which is the finite element method.

The next question is how many units to divide the aircraft into. With a natural mesh model, the unit size is relatively large, meaning that almost every independent part is calculated together.

Fine mesh elements divide the aircraft into many small elements and calculate them separately. The smaller the size of the element, the more accurate the simulation results. When the East was developing the C919, it built a finite element model with tens of millions of units, which could include every single rivet, reaching the world's first-class level!
However, this requires powerful computing capabilities! Millions of cells were only achieved two thousand years later; by the late 1970s, having a finer grid with tens of thousands of cells was already quite impressive!

"Back then, the product from the strongest military aircraft R&D unit in China suffered from poor calculations. When it was put on the static test bench, the aircraft disintegrated when the load reached 92%..."

"Which organization is this? They're so unlucky!"

"That's right, we have to avoid this when we're assigned jobs after graduation..."

"Dear students, I'm not telling you this as a joke. Now we have computers that can perform calculations at this level. Even if our predecessors in other organizations knew how to do it, they didn't have the necessary conditions. They conducted their research under difficult conditions, and their spirit is something we should learn from!"

After saying this, Qin Liang glanced at Professor Liu, who was giving him a meaningful look, before turning his head back. He then saw several people standing at the door, with the leader looking at him with a complicated expression.

"Mr. Gu? What brings you here?" Qin Liang's face lit up with surprise. "Did you come here specifically to inspect our server room?" "Liangzi, what you just said really made me think. Back then, we didn't have the conditions, so we took many detours. Now that we have the conditions, we can definitely develop advanced fighter jets much better. Don't you think so?"

"Yes, Mr. Gu, you're right."

"You just said there aren't any missions right now?"

"Ahem, how could there be no task? I'm just worried that the students might feel pressured..."

"We want to entrust all the massive computing tasks in the North to you. I heard from Lao Huang that you offered several million to modify the flaps for our project?"

"Well, I was just saying it casually at the time. Mr. Gu, since you're here for this matter, how about we make it cheaper, two million eight hundred and eighty thousand?"

"What?" Zhao Guangming, who had come over next to Elder Gu, was furious: "You really think we, the Northern Institute, are easy prey? Our Northern Institute is the number one military aircraft research institute in the country..."

"Old Zhao!" Old Gu stopped him and continued looking at Qin Liang: "I just heard that you're going to use a computer to calculate the finite element model and complete the static calculation of the whole aircraft. Our J-8 is being modified for the nose, so we need to recalculate. If we assign this task to you..."

"Then let's do another 288. Since I proposed this project, I can't let you have it difficult. We'll calculate the nose section in one month! Actually, calculating the nose section is much more complicated than adding flaps to the wings. Northwestern Polytechnical University can afford to take a small loss, but we can't make more money off you, right?"

288, all for 288, you won't lose out, you won't be cheated!
Everyone else was stunned. In this era when a monthly salary was only a few dozen yuan, having five yuan in your pocket would make you extremely happy. No one present had ever seen tens of thousands of yuan at once. But now, the projects Qin Liang was discussing with Bei Fang were worth millions!

Zhao Guangming's face darkened. That's right, they've taken our Northern Bureau for a fool!

"It's so expensive, we should at least replace the double delta wings on our J-8 fighters!"

"The purpose of the double delta wing is to increase maneuverability. Our J-8 has a slender fuselage and was originally designed as an interceptor. If we switch to a double delta wing, the drag will increase and the speed will decrease. The fuselage will not be able to withstand high overloads, so what's the point? Installing flaps is to improve takeoff and landing performance. My friend, since you are an engineer from the Northern Institute, you should understand this principle!"

Old Gu nodded: "That's right, the J-8 is indeed not suitable for a double delta wing. However, could you also help us recalculate the data for the rear fuselage?"

I've already bought two 288s, can I buy another one?
"If it's just a matter of recalculating, then we'll help you with that. But... Mr. Gu, would you like to use the supersonic area rule to reshape the rear fuselage? If you're willing, another 288 would be enough."

(End of this chapter)