Young people who have just joined the work are often more passionate, not to mention that they have been personally guided by Chang Haonan.

The nose side wing is a relatively independent aerodynamic component, due to its relatively small size, so when flying in level flight or low angle of attack, it will be in a state of contraction, which will not affect the normal aerodynamic shape of the aircraft, and will only start and play a role when the angle of attack breaks through a certain threshold.

And this process is obviously impossible to carry out manually by the pilot.

Therefore, when the threshold is set at what position, and the length and width of the nose edge strip are respectively, the best edge strip vortex can be obtained, which is the "operation" left to Lin Tongxin.

As for Sun Huizhong himself, he naturally has to be responsible for more important tasks-

Under the guidance of Chang Haonan, the design and optimization of the inlet channel of the advanced training aircraft DSI was completed.

As a completely non-adjustable type of air intake, the biggest problem with the DSI air intake from the mother's womb is that there is only one configuration, so the optimization interval is constant, and it must have a large optimization interval width.

It doesn't matter if the optimal optimization range of the rectangular bulkhead air intake is only Mach 0.01, anyway, as long as the flight controller is strong enough, the position of the bulkhead can be adjusted to ensure that the intake efficiency is always at the optimum.

However, if the fixed air intake is made like this, a slight change in the flight speed will lead to a sharp decrease in the air intake efficiency, and even the attached surface layer cannot be blown off, resulting in strong air intake distortion and thus affecting flight safety.

In short, a high level of design and experience is required to achieve a satisfactory optimization of an aircraft using the DSI intake.

Moreover, Project 10, as a key project at the highest level, will attract the attention of countless people in every move.

After the first flight of the prototype 01 with a ternary adjustable air intake, it had to be overhauled, and it would have to come up with convincing data.

And it just so happens that the common speed range of the advanced training aircraft is much smaller than that of the fighter, and the optimization difficulty of the relatively traditional aerodynamic layout is lower than that of the J-10 using the canard wing + large delta wing configuration.

It is the perfect practice session.

"Sun Gong, what I'm going to talk about next, you must make sure you fully understand, if you don't understand something, ask me immediately."

Chang Haonan turned on his computer, called up several design files that had been prepared a long time ago, and then motioned for Sun Huizhong to move two chairs from the side.

For him now, many times he doesn't have to do everything himself, especially when he has a helper by his side.

"Understood."

Sun Huizhong quickly sat down next to him.

"Regarding the basic principle of the DSI inlet channel, I have already talked about it when I was in Rongcheng, simply put, it is to use the characteristics of the conical shock wave itself to form a strong pressure gradient on the convex hull surface at the lip of the inlet channel, and blow the surface layer of the fuselage at this position directly outside the air inlet opening, so as to reduce the adverse impact of the surface layer on the air intake efficiency."

Speaking of which, Chang Haonan called up a pressure distribution map that he asked Yao Mengna to help draw some time ago, which was tested with a DSI inlet model in an ideal state.

It can be clearly seen from the above that the convex hull structure uses the pressure difference to "push" the shock wave directly.

After making sure that Sun Huizhong and Lin Tongxin had no doubts, he officially entered the design part of today's focus:

"From this principle, it can be seen that the core of the design of the DSI inlet is the shape of the convex hull structure, and through the theoretical and numerical analysis of the waverider body, I have summarized two methods of designing the convex hull."

"I think you said before that you select a number of tracking points from the leading edge of the conical plane, and trace downstream of the flow field from these tracking points in the flow field......"

I have to say that Sun Huizhong was definitely attentive in Rongcheng at that time.

Even such details can be remembered.

"That's right, this is the generative body method, also known as the cone guide method, and it is also the basic principle of the most traditional method of designing the DSI inlet tract, which is relatively intuitive and easy to understand, and the design process is less computational, so at the beginning of this year, it was the first method I considered."

Chang Haonan nodded, but then said in a changed tone:

"But recently, I just designed a new numerical calculation tool that is much more computationally efficient than traditional software, so that the limitation on the amount of computation has become much smaller, so I have developed a second method on the basis of the generative body method, the close cone method."

"...... The second way? ”

Sun Huizhong felt that his brain was a little insufficient at this time.

Designing the DSI intake duct is inherently a difficult task, and even the United States has only installed a relatively simple early version of the F16 on an improved technical demonstrator.

The JSF Joint Strike Fighter, the first mass-produced fighter to use the DSI air intake, is only now being selected.

In short, it is still in the exploration stage of design.

As a result, you have summed up a complete set of methodology, not to mention, but also includes two solutions?

It's just unreasonable......

"That's right, the second method is more accurate than the generative body method, because this method does not need to assume a geometry in advance, but directly gives a curve describing the shape of the shock wave at the exit of the waverider body, and divides this curve into countless small arcs, each arc can be considered as a part of the shock curve, and the cone that produces the shock wave is the close cone, and the plane that is too close to the axis of the cone and orthogonal to the arc is called the close plane ......"

“……”

"A close cone is obtained on each arc of the shock curve, and finally a series of streamlines are obtained by defining the leading edge curve, which are combined to form the lower surface of the DSI inlet convex hull."

"This design is more flexible and can meet the requirements of a wide range of flow rates and a variety of inlet geometries, which means that different shock curves can be adjusted to suit any engine without having to accommodate the engine intake tract, and the final product will naturally perform better."

Speaking of this, Chang Haonan turned his head and saw two pairs of simple eyes.

Obviously, the leap of thinking just now seems to be a bit big.

It is indeed difficult for engineers with average mathematical theory to fully accept the principles in a short period of time.

"Let's do the math in two ways."

He is going to demonstrate it in the simplest way:

"Let's assume that the shape of the inlet shock wave is a quadratic curve z=-ax^2+b(a>0)."

Chang Haonan wrote a quadratic function directly on paper.

"Uh...... Director Chang, the shape of the shock wave is so simple......"

Taking advantage of Chang Haonan's efforts to bow his head and write, Lin Tongxin originally wanted to ask why the shock curve was such a simple form.

But it came to an abrupt end in the middle of the conversation.

Because Chang Haonan wrote down the second function on paper.

"And such a combination of parametric equation curves."

Chang Haonan stopped his pen and looked at Lin Tongxin who was standing next to him:

"What were you just asking?"

"No, it's fine."

The latter quickly shook his head:

"I'm just thinking, Director Chang, it's amazing that you can come up with such a complex shock curve."

Hurt.

It hurts.

My face hurts......

And Sun Huizhong next to him had an expression of "I don't really want to know this person".

In fact, Chang Haonan didn't hear what the other party was saying clearly just now, so he just continued to introduce:

"The design of the convex hull surface is originally the core step of the DSI inlet channel, and I have thought of using the conic curve equation to represent it alone, but it is still too difficult to derive the form of the shock curve formed from the mechanism in terms of the current computing power, so I have to add some parametric parts."

"I see."

Lin Tongxin now only hopes that this topic will pass quickly.

It was so embarrassing, he wanted to escape from this world just now.

Fortunately, Chang Haonan did not continue to entangle:

"Then it's just a matter of ......"

He spent more than ten minutes on the computer, actually demonstrating the steps he had just said.

Of course, for the sake of convenience, all parameters are temporarily selected as 1, so the design of the convex hull shape is a bit strange.

However, judging from the reactions of the two people next to him, at least the purpose of the explanation was achieved.

So Chang Haonan picked up the pen again and circled several symbols such as A, B, L, and β:

"Our next work, to sum up, is actually to select the appropriate parameters for this shock curve according to the characteristics of the aircraft."

Then he looked at Lin Tongxin next to him again, but this time he changed to a more relaxed tone:

"This is another reason why I don't want to extend the length of the side strip under the canopy, because the incoming flow compression effect of the side strip will destroy the otherwise clean shock shape of the air intake, making it difficult for me to characterize the convex hull shape corresponding to different shock curves in the design process, and the air intake will not have this problem if it is designed directly in front of the side strip."

"Got it now?"

Lin Tongxin nodded hurriedly.

He's learned not to give his opinion casually until he's finalizing his thoughts.

"That's good, if there are no other questions, we'll be ready to start work, but even if you don't understand anything later, you can always ask me."

Chang Haonan said and fastened the lid of the laptop, got up and prepared to take the two people to the computer room:

"Although I did propose this model for the purpose of technical verification for Project 10 at the beginning, if nothing else, Guihang will be the first aircraft manufacturer to use DSI air intakes on production aircraft."

He knew that Huaxia in this era had a deep obsession with striving for the "first" at all levels.

In the 20s of the 21st century, after the aviation industry has developed, it no longer deliberately does propaganda and guidance in this direction.

It can only be said that the more you lack something, the more you want something.

Sure enough, Sun Huizhong and Lin Tongxin, who heard his words, were in good spirits, and the little tiredness they had just shown disappeared in an instant.

"Can it be faster than the United States?"

The latter immediately asked excitedly.

"Of course, the JSF project has not yet been skimmed, and there is a high probability that your model will be able to make its first flight before the end of this year."

Chang Haonan packed up his things and motioned for the other two to follow him.

"This ......"

Lin Tongxin was stunned by this time node.

He remembers that when he was in school, his teacher said that the cycle of designing an airplane was often several years or even more than ten years.

"Master, is our Guihang's efficiency so high?"

Because Chang Haonan had already walked to the front, he had to whisper to Sun Huizhong next to him.

The latter was almost amused by him:

"There are indeed people who are very efficient, but it's not our Guihang."

After speaking, he looked at Chang Haonan's back and quickly followed.

"Hiss......"

Lin Tongxin gasped:

"Director Chang is a little scary......"

(End of chapter)