Chapter 74 Designing a Flying Machine
Xu Yuan had a general understanding of the test paper. After filling in the candidate information, he calmed down and started to work seriously. Soon he entered a state of deep learning as if he was cut off from the outside world.

As a professor at the Institute of Fluid Mechanics, Xu Chongxing is very good at setting questions.

Unlike the theoretical mechanics questions answered by other candidates, each question in Xu Yuan's test paper often involves several professional knowledge at the same time.

If the basic knowledge of each professional course is not up to standard, it is impossible to give accurate answers.

It was obvious that Xu Chongxing decided to set the questions himself without thinking that Xu Yuan would be able to pass the exam. Unfortunately, he underestimated Xu Yuan's solid foundation and rich experience in engineering mechanics.

With the added bonus of mathematical knowledge, it didn’t take long for me to easily complete the big calculation questions that followed.

"A horizontal force F acts on point B of the steel frame, as shown in the figure. If the weight of the steel frame is ignored, find the restraining forces at supports A and D."

After reading the question silently in your mind, you will know that the content involved is statics. Based on the known conditions, you can determine the research object and draw the force diagram.

Solve by determining the force series equation.

It may be because the first big question is too simple and there is a big gap between it and the previous ones in terms of complexity.

Xu Yuan also expressed doubts about this.

"This level of difficulty shouldn't be possible. Could it be that Professor Xu let us off easy?"

Judging from the previous question types, the difficulty of the entire test paper is definitely not low, and it does not seem to be a deliberate way of letting the test go.

The key point is that this calculation problem is very easy, which makes it difficult to guess Xu Chongxing’s intention.

However, this doubt did not bother Xu Yuan for too long. After finishing the next few calculation questions, he found that the difficulty was gradually increasing.

The big statics question at the front was just an appetizer, a warm-up for him.

As the last calculation question came into view, Xu Yuan couldn't help but frown slightly.

“Please design an aircraft shape.”

Although the entire question is only a short sentence, its difficulty is far greater than all the previous large questions.

For an aircraft to be able to travel in the atmosphere, flight speed and structural safety are both key.

Its appearance design involves fluid mechanics, aerodynamics, and structural mechanics.

The examiner can judge the candidate's mastery of professional knowledge and whether he or she has a relatively high talent in this field based on the rationality of the designed appearance.

Xu Yuan certainly didn't expect Xu Chongxing to ask such a question, but although it was unexpected, it didn't stump him.

When he studied fluid mechanics in his previous life, he also delved into the professional design of advanced aviation vehicles.

The thought stayed here, and he immediately picked up the pen again and simply drew a structural outline of an aircraft.

Then explain your design concept.

The aircraft designed by Xu Yuan boldly chose to adopt the unpopular canard layout.

The so-called canard layout is an aerodynamic layout suitable for supersonic air combat.

By moving the horizontal tail to the sides of the nose in front of the main wing, the same operating performance can be achieved with a smaller wing surface.

Simply put, using this type of layout can improve the aircraft's lift-to-drag ratio at large angles of attack.

Save engine thrust.

It is only because the aerodynamic characteristics of the canard are unstable and require a strict flight control system to support it that it has been buried in the long history of aircraft design.

Even the F-16 chief designer Chiralek gave a famous comment.

"The best place for a canard is on an enemy aircraft."

But Xu Yuan is well aware that the prejudice against canards is historically limited.

In his design, he took the approach of blending the canard, wing slats and lifting body together.

To make up for the defects of the canard.

As a freshman, he was definitely not qualified to participate in the design and research of aircraft. Today, he took this opportunity to simply draw a new canard aerodynamic layout. As for what kind of chemical reaction would be produced, he had no idea.

In short, he mastered this last big calculation question.

Due to limited conditions, he simply drew a rough outline of the structural and aerodynamic layout design to provide an explanation.

If I really want to complete the entire appearance design, I'm afraid I'll need a thick stack of design drafts.

After Xu Yuan finished answering all the questions, he put down his pen, straightened his body, took a breath, and then raised his hand to signal the invigilator.

"teacher."

"I want to hand in my paper."

The invigilator sitting on the podium noticed Xu Yuan's actions and immediately frowned and reminded him.

"Your test paper is special. You can hand it in half an hour at night. This is what Professor Xu said."

Anyone who knows Xu Chongxing's level will not believe that a freshman who has just been in school for half a semester can finish all the questions set by Xu Chongxing himself.

What's more, this student has never attended any classes at all.

If you choose to hand in the paper early at this time, it definitely means that you feel the test questions are too difficult and you are giving up on it.

Although this result is not surprising, as a teacher I certainly don't want students to give up so easily.

Even if you feel it is really difficult, you should persevere until the last moment.

At least it's not shameful.

Just when he was about to persuade Xu Yuan, the next second he heard Xu Yuan's confident voice.

"No need, I've finished it." Upon hearing this, the invigilator immediately showed a shocked expression on his face, and looked at Xu Yuan with some disbelief.

"real or fake?"

He blurted out a few words subconsciously, then hurriedly walked down the podium and walked towards Xu Yuan.

At this moment, everyone else in the classroom raised their eyes at the same time, and question marks slowly formed in their minds when they saw Xu Yuan's actions.

This is too much boasting.

I still have a few big questions left on this ordinary test paper, and you tell me that I have finished the test paper given by Professor Xu?
Almost everyone held this idea and didn't think what Xu Yuan said was true.

Everyone knows that Xu Yuan is very good at mathematics, but at present he is only studying engineering mechanics. The key point is that they all know that Xu Yuan has only been to the Engineering Mechanics Department a few times since the beginning of the school year.

Under such circumstances, even if Xu Chongxing himself came, he would not believe that I could finish the test paper given by Professor Xu Chongxing.

Just as everyone stopped writing and waited for the follow-up, the invigilator reached out and picked up the test paper on the table, then immediately lowered his eyes to examine it carefully.

At a glance, you can see that there are no blank questions on the test paper, especially the spaces for calculation questions are filled with words.

As a professional course teacher, he could naturally judge whether Xu Yuan's answer was correct or not. His pupils trembled and he was extremely surprised.

These professional teachers have basically no different views from Xu Chongxing.

Everyone thought that Xu Yuan relied on his talent in mathematics and overestimated himself, so he chose to pursue two professional degree courses at the same time.

As a result, after school started, Xu Yuan focused too much on mathematics, resulting in him being unable to attend classes in the Department of Engineering Mechanics.

Rather than being unable to find a balance like I am now, I might as well devote all my time to mathematics.

It's a good time to strike while the iron is hot and continue studying difficult mathematical problems.

But now after seeing Xu Yuan's test paper, he suddenly felt that there might be some misunderstanding.

The reason why Xu Yuan didn't come to class was because he had already mastered the course.

A lot of thoughts flashed through his mind quickly. The invigilator realized that the exam was still going on, so he quickly came to his senses and responded calmly.

Agree to let Xu Yuan hand in his paper early.

"you can go now."

However, when he said this, his expression was obviously more smiling than before.

Unlike national exams such as the college entrance examination, there are not too strict regulations for midterm and final exams in college.

After submitting your paper early, you can leave the examination room directly without having to wait in the designated lounge for the end of the exam.

Xu Yuan watched his test paper being taken away and did not linger any longer. He simply packed up the stationery on the desk and got up to leave.

But when other people saw this scene, they found it even more puzzling. They didn't expect that the invigilator would let Xu Yuan hand in his paper early so easily. They didn't know what level of work he had done on this test paper.

"Have you handed in your paper already?"

"Could it be true that he has finished all the questions on the test paper as he said?"

"That was a question from Professor Xu. How is that possible?"

"I guess the questions were too difficult so I just gave up."

"Have you ever thought about this? He can even prove difficult math problems. I don't think it's surprising that he finished the test paper."

……

The invigilator heard the whispers from below and suddenly turned around and resumed his stern expression to reprimand.

"During the exam, no talking is allowed. Also, I would like to remind you that there is not much time left before the exam is due."

As soon as these words were spoken, everyone in the room fell silent. Only then did they realize that they were so busy looking at other people's test papers that they hadn't even finished their own.

Thinking that they might have to retake the exam, they all focused on the test paper and worked hard to answer the questions.

Xu Yuan was the first to return to the dormitory. He sat at his desk and waited for a while before seeing Li Zhenya, Wang Haitao, and Liu Yang coming back from their exams. It seemed that they had done well in the math analysis exam in the morning. They heard voices before they entered the dormitory.

After pushing the door open, Xu Yuan smiled and asked, "How did you do on the exam?"

"Brother Yuan, you are amazing. The questions you explained to us earlier were actually tested in today's exam."

Wang Haitao saw that Xu Yuan was too busy putting his things down, and immediately responded excitedly when he heard this.

"I think I have passed the mathematical analysis exam." Li Zhenya also added.

After listening to what the two said, Xu Yuan realized that a question of the same type as the one he had talked about appeared in the math analysis test paper in the morning. This would definitely not be difficult for Li Zhenya and Wang Haitao.

As a result, my self-confidence has increased a lot.

Xu Yuan thought this was a good thing. At least having confidence was better than worrying about failing a course every day.

Liu Yang next to him naturally had nothing to say. With his level, it was relatively easy to cope with an exam of this level.

Soon everyone realized how fast Xu Yuan was at answering questions, and they all expressed their concerns out of curiosity.

"Brother Yuan, you finished the exam so soon?"

"It wasn't very difficult. I handed in the paper early after finishing it, and I didn't have to take the next exam."

In response to Liu Yang's question, Xu Yuan gave an indifferent reply, not thinking that this matter was worth talking about.

On the contrary, Li Zhenya and Wang Haitao looked envious after hearing this. They were looking forward to not having to take part in the subsequent advanced level examination.

(End of this chapter)