According to the traditional customs of the Chinese, when the guest goes to the host's house, the host stays the guest, of course, the guest cannot stay immediately, and has to be polite a few times, and under the repeated retention of the host, the guest has to agree to stay with great graciude. Therefore, in the living room of Shen Yi's family, of course, this scene must be staged exactly as it is. This cannot be said to be the Chinese fake politeness and real hypocrisy. In fact, isn't the process of human beings inventing all kinds of etiquette just to look good and get by? This set, not only we Chinese are poor and exquisite, but foreigners also attach great importance to etiquette. In any country, if you don't follow the rules and don't pay attention to etiquette, you will listen to it nicely, or if others want to praise you for a certain purpose, they will say that you are really rude and uneducated, but behind the scenes, they will definitely say that this person is really rude and uneducated.

Therefore, in fact, the old man Xiao Yizhan is not necessarily unwilling to stay. You must know that he is now aware of Shen Yiyi's formulas, and he is still thinking about what else he can take out of Shen Yiyi's brain, so that he can go home now, he is really unsatisfied. And Luo Yu is not to mention, he has worked hard to calculate the hot results of the new oven for a few days, if he can't show it in front of others, then his heart will be like a cat scratching, don't mention the uncomfortable energy.

After Shen Yiyi repeatedly retained, and even Shen's mother saw that the guests were leaving, and came out of the kitchen to say that she would not let the guests go, Xiao Yizhan and his grandchildren sat down again and continued their academic discussion with Shen Yiyi.

Luo Yu was finally liberated. He excitedly took out a stack of paper from his bag, on which were drawn the airfoils he had preliminarily selected, and of course, the calculations of him and Old Man Xiao in the past few days. Xiao Yizhan looked at his grandson's excitement, and knew in his heart that his grandson seemed to be suffocated because he had just discussed the origin of the formula with Shen Yiyi. It's good now, too. Let him tell him about his own great achievements in the past few days. In fact, the old man Xiao Yizhan now also wants to see what kind of thinking Shen Yiyi will follow for the low-speed wing shape of these wings made by Luo Yu to carry out the next step.

Shen Yiyi's skills on the basis of fluid mechanics and the insight to derive new formulas from empirical formulas have deeply impressed Old Man Xiao. But Old Man Xiao still wanted to see Shen Yiyi's amazing insight. There was no surprise in the performance. He was already thinking about whether to report the matter of Shen Yiyi, a little genius, with a few old guys. At any time, for a country, outstanding talents should also be protected and cultivated.

Shen Yiyi followed Luo Yu's fingers and looked at these wings, and as far as his eye could see, there was the calculation process written on the paper on the edges of these wings. Looking at those numbers, Shen Yi thought to himself, Luo Yu has been tired enough these days. Just looking at this dense number crowded in a pile, I felt my scalp tingle and didn't want to look at it anymore. But Luo Yu even exceeded his expectations and even counted two more airfoils, it seems that in terms of calculation. He was genuinely interested.

However, Shen Yiyi will not forget his task today. So while listening to Luo Yu's introduction, she also reached out and took out the other papers to see. She picked out the content she was interested in and carefully looked back and forth. Looking at it, although Luo Yu was still there and constantly introducing, Shen Yiyi already had an idea in his heart.

Xiao Yizhan watched on the side that Shen Yiyi was already watching the results by himself, and he didn't listen carefully to his grandson's explanation, but he didn't stop his grandson's introduction, although he was a little unbearable to his grandson, he still nodded in his heart. This little girl seems to know how to do things. In fact, Old Man Xiao himself thinks that this kind of calculation document. Since there is a clear formula, you don't need to introduce it to understand it. However, if you don't let the calculator introduce you, it will be a blow to people's enthusiasm, so it is often arranged purely for the purpose of unity. But let's be honest, it's true that such an introduction is not necessary.

Luo Yu introduced it for a while. also found that Shen Yiyi was already reading the content behind, and he himself realized that most of the words he said were repetitive content, and there seemed to be no need to say any more. I stopped by myself.

As soon as Shen Yi saw him stop, he asked casually: "Why did you stop?" You're not going on? ”

Luo Yu said dejectedly: "Don't say it." You're not listening anyway. There was still a bit of anger in the tone of his voice.

Shen Yiyi smiled and said, "Ha Luha." Look at the look of your little nose and eyes. After speaking, his face turned straight and he said, "Luo Yu, I don't need to listen to your introduction, just seeing these numbers on the sides of these few pieces of paper, so many numbers, such a dense line spacing, I know what an important and arduous work you have completed." I would like to thank you for your efforts. Without your hard work, we wouldn't have been able to take the first step in this project. So I must thank you. As he spoke, he really stood up and bowed deeply in the direction of Luo Yu and Xiao Yizhan.

Seeing that she suddenly became so formal, Luo Yu was really a little unaccustomed, and even a little at a loss, just muttered: "This...... Not like that anymore. Seeing that Old Man Xiao shook his head, this kid is really tender. These few words repaid his efforts at once, and it really made him embarrassed. Compared with other little girls, there is really a gap between this kid and other girls. But then again, this little girl Shen Yiyi really speaks with the flavor of leadership, and I don't know if it's a family history.

There was a faint dissatisfaction with the fact that his grandson was compared to the little girl in his heart, and Old Man Xiao opened his mouth and asked: "Classmate Shen Yiyi, you have read the results of so many calculations, do you have any specific thoughts in your heart now?" It doesn't necessarily mean that all seven airfoils were chosen, right? ”

Shen Yi nodded a little, and said as a matter of course: "Of course, I won't choose all seven at once." In fact, I have already chosen two options that we will do next. I'll point it out right away, and I ask you to refer to it for more time. ”

Xiao Yizhan nodded, in fact, he chose one more from these seven, but after listening to Shen Yiyi say that he chose two, he didn't know if there was any intersection between Lu Dao.

Shen Yiyi picked out two wings from these pieces of paper: "Luo Yu, and Xiao Lao, you see, these are the two I selected." Following the direction of her finger, the grandfather and grandson looked over.

"Hey, how did you choose these two? These two don't have the biggest lift. You see, I obviously gave you a few more lifts, why didn't you choose them? Luo Yu raised an objection at the first time. It's not that he thinks he's really made the wrong choice. He now thinks that Shen Yiyi is better than him in terms of learning, so he can't be sure that Shen Yiyi's choice is wrong. He just wanted to understand the reason why Shen Yiyi chose this way, with the purpose of learning.

Shen Yiyi patiently explained: "That's right, the lift you calculated is indeed greater than this. But those are the ultimate lift, and if you draw the lift and the corresponding flight speed as a curve, you will find that the greater lift you mentioned in the realization occurs at a distance from the 50 km/h speed I told you, and the two airfoils I chose, you see, have the highest lift near 50 km/h. As Shen Yiyi drew the curve of the corresponding airfoil on the paper, Luo Yu immediately understood the reason why Shen Yiyi chose such two airfoils. He nodded knowingly, indicating that he understood.

Shen Yiyi continued: "So, Luo Yu, the combination of aircraft design and power is very important. Our airfoil was designed to fly at 50 km/h, so we couldn't forget that during the design process. ”

Xiao Yizhan nodded secretly, the little girl's thinking is still very clear. However, he still deliberately proposed: "If you say so, classmate Shen Yiyi, why don't you choose this one?" According to you, isn't this airfoil also the most lifting in the range of 50 km/h? And at lower speeds, the lift ratio is also the highest. He asked the question with some smugness. He didn't want to see Shen Yiyi's jokes, but just felt that Shen Yiyi was so young and talented, and he couldn't make her arrogant, lest she not seek to be motivated. So he also had to knock her at the right time to see how she would react if she found out that she had missed a plan.

Shen Yiyi glanced at the plan pointed out by the old man and smiled: "Oh, it's this plan." Xiao Lao, you are not wrong, it is true that the speed rise ratio of this scheme in the low-speed section is relatively large. Xiao Lao was a little proud when he heard this, and said in his heart, you found that you were insufficient, but Shen Yiyi continued, "But the biggest problem with this plan is that there are sharp shape transitions in the airfoil. Our paramotor is made of flexible material and is inflated, which means that the shape of the wing will change if it is subjected to force. However, the high lift force at low speeds means that the force acting on the surface of the wing increases, and deformation is likely to occur. And this airfoil is very sensitive to deformation, and a small deformation can bring a huge change in lift, and even cause danger. So after weighing it again, this airfoil still gave up. ”

Shen Yiyi said calmly, but the old man Xiao Yizhan's expression changed greatly. He went so far as to forget that this was the design of the paramotor, and not of the aircraft. The difference in materials and principles between paramotor and aircraft wings will of course have an impact on the choice of airfoil. But as an expert who has studied this profession for so many years, he has forgotten such a basic thing and still wants to see other people's jokes, thinking of this, he is really ashamed.

Shen Yiyi didn't want to embarrass the old man, and said politely: "Old Xiao, presumably you raised this question to test my consideration of the material characteristics when designing." I think my answer should be able to meet your requirements now, right? (To be continued......)

PS: Well, there are details about the technique, and I can only say that there is such a possibility. As the old saying goes, vote, bookmark and subscribe. It's early today, ha.