Li Zhen raised his hand and stretched out an index finger.

He has mastered the way of lecturing, and understands that when lecturing, it is easier to deepen the impression of everyone with body movements.

"Remember, I'm going to talk about the theorem. In fluid mechanics, it is necessary to apply the continuum hypothesis, the mass conservation theorem, the energy conservation theorem, the momentum theorem, the stress tensor, and the viscosity hypothesis. Questions are allowed. ”

After Li Zhen finished speaking, he put down the triangular ruler and looked up. A group of people writing notes with their heads down.

When they finished writing their notes, in an instant, everyone raised their hands.

Hou Qiang asked.

Hou Qiang hurriedly stood up, and her tone was extremely fast: "What is a sticky hypothesis?" ”

Li Zhen naturally knew that many of these theorems had not been told to them, but Li Zhen couldn't remember which ones had been said and which ones had not been said, so he gave everyone the opportunity to ask questions:

"Sticky assumptions. The stress exerted on the fluid and the resulting rate of deformation are linked by a certain relationship between a macroscopic property of the fluid, which is manifested as the internal friction of the fluid, which is the assumption of viscosity. Due to the viscous energy dissipation, the fluid will gradually stop moving without external energy replenishment. Viscosity plays an important role in the movement of the fluid near the surface of the object, so that the flow velocity decreases layer by layer and is zero on the surface of the object, and the fluid can also be removed from the surface of the object under certain conditions. This is the sticky assumption. ”

Li Zhen paused word by word, and said as slowly as possible in his tone.

A group of people took a deep breath, didn't even dare to breathe, and frantically picked up the pen to record.

This paragraph is too long, you have to hurry up, if you don't hurry up, you will forget it later.

Lin Xiufeng's eyes were red and bloodshot at this moment, and his whole heart was roaring, and he was about to collapse.

He had never felt such a strong pressure, obviously he was auditing a class, and when he heard it on the ground, the whole person was going crazy. Want to roar, slow down, slow down. Slow down, I didn't hear clearly.

The other teachers are going crazy too, and their hands are going to be broken. This rapid writing is a kind of torture, and you have to write at the same speed as his speech. When talking about concepts, you can also pick and choose key points to remember, but when it comes to theorems, not a word is missing.

'Rustle', don't say desertion in class.

In Li Zhen's class, you can't even afford to waste time scratching your head.

Continue to ask questions. Lan Xuncao. ”

Lan Xunke, the first batch of personnel of the Kyushu Institute of Physics, hurriedly stood up: "What is the continuum hypothesis? ”

"Matter is made up of molecules, even though the molecules are discretely distributed and move in random heat. But in fact, in a very small range, the mean value of the microclusters of fluid molecules that do thermal motion is stable. Therefore, it can be assumed that fluids are composed of continuous substances, in which physical quantities such as temperature, density, and pressure are continuously distributed scalar fields. ”

"Keep asking."

"What is the law of conservation of mass?"

"In a chemical reaction, the sum of the masses of the substances participating in the reaction is equal to the sum of the masses of the substances produced after the reaction. This law is called the law of conservation of mass. It can also be called the law of the immortality of matter. This is one of the fundamental laws that prevail in nature. I would like to emphasize here that we should not confuse mass with conservation of energy. ”

Li Zhen took a sip of water from the cup and moistened his throat: "To put it simply, the conservation of mass is talking about "mass", that is, the total mass of the reactants is equal to the total mass of the products; Conservation of energy refers to "energy", i.e., the total energy of the reactant is equal to the total energy of the product plus the total energy absorbed or released. One is quality, the other is energy, don't mess up. ”

"I ask, what is the law of conservation of energy?" Lin Xiufeng shouted.

Li Zhen glanced at him and said lightly: "The content that has nothing to do with this class will be discussed with others after class." ”

It's very tactful.

But Lin Xiufeng understands what it means, that is, don't make trouble if you can't keep up with the progress. If you don't understand, ask someone else for advice after class, so as not to affect my time......

Lin Xiufeng smiled bitterly, he felt that he couldn't understand......

These theorems are unheard of and unseen.

In fact, the people of the Kyushu Institute of Physics can understand, and they don't need Li Zhen's detailed explanation. Li Zhen told them the concept, and they could roughly understand it. Then after class, everyone will discuss it together, and you will be able to understand it thoroughly.

Li Zhen said: "I will mainly talk about the stress tensor, the applied response, and the force of force. The concept of stress tensor is a bit vague for everyone......"

"The forces acting on fluid microelements mainly include surface force and volume force, and surface force and volume force are respectively ...... So they are bounded...... The stress is described by a second-order tensor and the inner product of the surface normal, and only three quantities of the second-order stress tensor are independent, so that the stress distribution at a point can be determined as long as the stresses on three different surfaces at a certain point are known......"

Everyone was going crazy, they didn't expect that the detailed explanation of this stress tensor would be so long. A record of holding your breath.

His hands are going to be broken.

For the next half hour, Li Zhen began to give examples and explain those theorems.

Then we started to talk about fluid mechanics.

"Fluid mechanics encompasses both the basic theories of the natural sciences and the applications of engineering and technical sciences. From the perspective of fluid forces, it can be divided into hydrostatics, fluid kinematics and fluid dynamics; From the study of different "mechanical models", there are ideal fluid dynamics, viscous fluid dynamics, incompressible fluid dynamics, compressible fluid dynamics, etc.......

"And there are many branches of fluid mechanics, so let's focus on it. Fluid mechanics covers: hydrodynamics, aerodynamics, osmomechanics, explosion mechanics, environmental fluid mechanics, biorheology, ......"

"Let's talk about the concept of these branches in general, starting with biological biology ......"

“……”

The lecture lasted for more than an hour, and Li Zhen looked at the time: "Okay, class is over." There is a lot of content to be talked about today, so let's consolidate it after class, and be sure to infiltrate all of today's content within tomorrow. If there is a need to memorize by rote, be sure to memorize it by rote. Class! ”

After speaking, Li Zhen took the triangular ruler and left.

Since these transferred teachers seem to be useless, Li Zhen doesn't count on them anymore. Should you go to class or class today, so as not to waste another day.

"Xie Li Shi!"

Everyone stood and bowed.

After Li Zhen left, the entire auditorium completely exploded.

Liu Jinghong took the notebook in his hand, stood on the table and shouted: "Who knows what that biological change is." I don't understand that. ”

"I don't understand a key point, why is explosion mechanics included in fluid mechanics? How can the shock wave of an explosion be a fluid? Li Shi just said, I don't understand, who told me about it. ”

"A notebook with legible handwriting, change. Whoever told me about a lesson I didn't understand before, I asked him to copy my handwriting and gave him a hundred coins! ”

"Who's going to change it with me? Whoever tells me about the conservation of mass, I would like to explain to him the stress tensor. ”

“……”

Those teachers were completely dumbfounded, and they completely listened to heaven!

They understand what the learning model of the Kyushu Academy of Sciences is.