Chapter 1308 Magnetohydrodynamics

Of course, the 240th Institute and Han Chenfeng were not really ready to get something for free.

Although Chang Haonan did not need the help of an institution specializing in plasma research at the moment, as the subsequent research gradually deepened, it was inevitable that he would not be able to do it with the less professional technical forces of the Aviation Power Group and the Mechanics Institute.

Therefore, to some extent, it can be said that Han Chenfeng really caught up with a good time point.

If it was a few months to a year later, when Chang Haonan really took the initiative to find a partner, the competitive pressure would be much greater:

"Since Director Han has been studying plasma-related issues for many years, he must be familiar with the theory of magnetohydrodynamics, right?"

Han Chenfeng was a little puzzled by this sudden question, but he immediately realized that this was actually equivalent to the other party giving a positive response.

So he nodded quickly:

"Of course, the description method used to describe the interaction between magnetic field and fluid is the most basic part of our work..."

Then he paused again, with a look of surprise in his eyes:

"But this is an approximate semi-theoretical and semi-empirical model... At least at this stage, related research basically assumes that the plasma Debye length is much smaller than its characteristic length, and it is still an ideal continuous medium... If it is in a laboratory, or even in a ground facility, then this premise can be considered to be approximately satisfied, but for an aircraft, it may not be so easy to directly calculate a reliable result, right?"

"No, no, no..."

Chang Haonan waved his hand after hearing this, stopping the other party from continuing:

"What you said is already It is the revised magnetohydrodynamics theory..."

"Revised?"

Han Chenfeng's surprise turned into confusion:

"If it is not revised, it means directly combining the N-S equations describing the laws of fluid motion with the basic Maxwell equations describing the electromagnetic field..."

He originally wanted to say that this was a complete return to the basics. Although the form is simple and beautiful, the solution of the N-S equation alone has been a huge problem that has troubled many generations of geniuses, not to mention the coupling of a Maxwell equation...

It is because it is impossible to conquer the theoretical equations of magnetohydrodynamics (MHD) theoretically that researchers have developed various more complex, narrower, but more operational revised forms.

If the equation can be solved directly, then at least 90% of researchers in related fields will no longer have to come to work in the future...

However, considering that the person in front of him has won the Fields Medal after all, Han Chenfeng still considered some possibilities:

"Hiss... Did you really solve the MHD equation?"

Although there was indeed a bit of a joke when he first asked, when he finished speaking, the pressure of unemployment had already enveloped his heart.

"Of course not..."

Chang Haonan also felt that the other party was just talking casually, so he smiled and gave a negative answer.

Although the expected answer was like this at the beginning, Han Chenfeng still secretly breathed a sigh of relief.

However, before he could regain his composure, Chang Haonan changed the subject:

"But you may have heard that I gave some regularity criteria for the N-S equation a few years ago... In simple terms, if the Leray-Hopf weak solution of the N-S equation satisfies certain special conditions, then the weak solution is smooth on the existence interval."

"I..."

Han Chenfeng was stuck in his words, and it took him a long time to catch his breath:

"Theoretical mathematics is not my main research area... So I can only say that I have heard some rumors, and I don't know much about the cause and effect..."

"In fact, there is no cause and effect... In fact, until a few months ago, Even I always feel that this proof is far from any application and is almost only of pure mathematical value. "

Chang Haonan seemed very frank:

"But after paying attention to the MHD equation, I gradually found that if the regularity of the high boundary value is fully utilized, the Bernoulli criterion can be avoided, so that the term corresponding to B in the MHD equation can be regarded as the external force term of the N-S equation, without considering the contradiction between the change of the Bernoulli integral along the streamline and the N-S equation under this assumption..."

This sentence is only a hundred words, but it made Han Chenfeng, who was sitting on another sofa on the side, start thinking rapidly.

Although his mathematical foundation is somewhat lacking and he cannot understand how the other party proved the smoothness of the weak solution, if he skips this step directly and believes in the correctness of this proof, then he can still figure out some of the later parts.

But Chang Haonan obviously didn't intend to keep the secret, and revealed the answer before Han Chenfeng understood all the links:

"It can be proved that for a steady incompressible fluid in a two-dimensional bounded domain, the solution of the MHD equation must exist... In this way, it is equivalent to removing the two most fatal assumptions based on the original plasma magnetofluid theory model..."

The words have already been said to this point, and the latter's originally messy thoughts in his mind were almost instantly sorted out:

"Don't you need to assume that plasma is a continuous medium, and don't you need to ignore the work done by pressure?"

"That's right!"

Chang Haonan stood up and strode back to the back of the desk:

"After excluding these two of the original eight basic assumptions, six are left. Among them, the mean free path of particle collision is much smaller than the characteristic line of plasma, the plasma is stable and axially symmetric, and only two kinds of charged particles, electrons and ions, are considered. Artificial plasma is inherently easy to satisfy.”

"The local thermodynamic equilibrium, single fluid characteristics and low magnetic field magnetic Reynolds number may be a big problem for those of you engaged in nuclear science, but the magnetic Reynolds number of the aircraft surface, let alone an ordinary aircraft, even for hypersonic flow It is less than one thousandth, and the ionization rate itself is negligible..."

When Chang Haonan's words ended, the office suddenly fell into silence.

Han Chenfeng could even clearly hear his own heartbeat that was accelerating:

"So, it can be calculated according to the two-dimensional axial symmetry model..."

Although there are still some purely mathematical parts in the middle that are not fully understood.

But he still felt completely transparent.

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As the saying goes, the more you know, the more you will discover your ignorance.

After investing in professional academic research, Han Chenfeng had almost forgotten the last time he had such a sudden enlightenment.

Although this is not his project and achievement, as a researcher in the field of plasma, there is nothing more exciting than hearing about an academic development that has real application value but will not cause him to lose his job. .

Perhaps to confirm Chang Haonan's statement, at this time, the laptop on the desk suddenly sounded a prompt.

Chang Haonan quickly clicked the mouse twice:

"The results from Yudu have been sent."

Han Chenfeng instinctively wanted to get up and go over to take a look, but he didn't know if he was within the knowledge range. As a result, he made a movement similar to Zamabu and stood still in mid-air. He didn't get up or sit back down. For a moment, he was quite Awkward.

But Chang Haonan didn't have so many worries. He turned the computer directly and motioned for the other party to take a look.

The Turbofan 10 plasma demonstrator was originally developed by Institute 606 and Institute 240. Otherwise, even if Chang Haonan was free, he would not have chosen a place like Huairou Science City to meet.

Han Chenfeng walked forward in three steps and then found that it was a radar reflection intensity curve with the abscissa axis as the angle and the ordinate axis as the decibel value.

Or to be precise, one is real and the other is imaginary.

But the distance is very close,

Especially the part corresponding to the middle 60-120° almost completely overlaps.

The legend below the coordinate axes states that the dashed lines are calculated values ​​and the solid lines are measured values.

Obviously, the difference between the two is almost negligible.

The picture has no sound, but it silently demonstrates the correctness of Chang Haonan's theory just now...

While marveling, Han Chenfeng thought to himself with regret:

"It's a pity that it's too different from the requirements of nuclear energy devices. Otherwise, I might really be able to see fusion power generation become a reality in my lifetime..."

Controllable nuclear fusion is said to be "half a century away from practicality", which shows how difficult it is to realize the project.

Sometimes, even researchers themselves inevitably wonder whether they are striving for an unattainable goal.

Chang Haonan, on the other hand, seemed to have seen through his inner thoughts, and made a sudden turn when he opened his mouth:

"Although it is not realistic to control fusion with the current theory, if you are willing, I have an idea to directly use plasma to generate electricity. Currently, I still lack someone to verify it..."