Li Zhen raised his hand and showed an index finger.
He has mastered the teaching method and understands that when lecturing, it is easier to make a deeper impression on everyone by adding body movements.
"Remember, I am going to talk about a theorem. In fluid mechanics, you need to apply: continuum hypothesis, mass conservation principle, energy conservation principle, momentum theorem, stress tensor, viscosity hypothesis. Questions are allowed."
After Li Zhen finished speaking, he put down the triangle ruler and looked up. A group of people writing notes with their heads down.
After they finished writing their notes, everyone suddenly raised their hands.
"Hou Qiang asked."
Hou Qiang stood up quickly and spoke very quickly: "What is the sticky hypothesis?"
Li Zhen naturally knew that many of these theorems had not been taught to them, but Li Zhen couldn't remember which ones had been taught and which ones had not, so he gave everyone a chance to ask questions:
"Viscosity hypothesis. The stress applied to the fluid and the resulting deformation rate are linked in a certain relationship to a macroscopic property of the fluid, which is manifested as the internal friction of the fluid. This is the hypothesis of viscosity. And due to the energy dissipation of viscosity Effect, without external energy supplement, the moving fluid will gradually stop. The viscosity plays an important role in the fluid movement near the surface of the object, causing the flow velocity to decrease layer by layer and become zero on the object surface. Under certain conditions, it can also Pulling the fluid away from the surface. This is the viscosity hypothesis."
Li Zhen spoke slowly and slowly.
'Shashasha' A group of people took a deep breath, not even daring to breathe out, and frantically picked up their pens to record.
This section is too long, so you have to do it quickly. If you don’t do it quickly, 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 strong pressure. He was obviously observing a class, and when he was on the ground, he was going crazy. If you want to roar, slow down, then slow down. Slow down, I didn't hear you clearly.
All the other teachers are going crazy and their hands are about to break. This fast writing is simply a kind of torture. Your writing speed must be equal to his speaking speed. When talking about concepts, you can pick key points to remember, but when talking about theorems, you can't miss a word.
'Shashasha' Don't talk about deserting in class.
In Li Zhen's class, you didn't even want to waste time scratching your head.
"Continue to ask questions. Lan Xunqing."
Lan Xunyan, a member of the first batch of the Kyushu Institute of Physics, stood up in a hurry: "What is the continuum hypothesis?"
"Substances are all composed of molecules. Although the molecules are discretely distributed and undergo irregular thermal motion. But in fact, within a small range, the mean value of the fluid molecule micelles undergoing thermal motion is stable. Therefore, it can be assumed that Fluid is composed of continuous matter, in which physical quantities such as temperature, density, pressure, etc. are all continuously distributed scalar fields."
"Keep asking questions."
"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 basic laws ubiquitous in nature. . I would like to emphasize here that everyone should not confuse the mass response with the conservation of energy."
Li Zhen picked up the cup and drank some water to moisten his throat: "Simply speaking, conservation of mass refers to "mass", that is, the total mass of reactants is equal to the total mass of products; conservation of energy refers to "energy", that is, the total mass of reactants The total energy is equal to the total energy of the product plus the total energy absorbed or released. One is mass and the other is energy. Don’t get confused.”
"Let me ask, what is the law of conservation of energy?" Lin Xiufeng shouted.
Li Zhen glanced at him and said calmly: "Anything unrelated to this class can be discussed with others after class."
It was said tactfully.
But Lin Xiufeng understood the meaning, that is, if you can't keep up with the progress, don't make trouble. If you don’t understand, just ask others for help after class. Don’t affect my time...
Lin Xiufeng smiled bitterly. He felt that he didn't even understand...
These various theorems are unheard of and unseen.
In fact, people at the Kyushu Institute of Physics can understand it, and they don't really 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 understand it thoroughly.
Li Zhen added: "I will mainly talk about the stress tensor, the application of stress, and the force of force. The concept of stress tensor is a bit vague for everyone... "
"The forces acting on fluid elements mainly include surface force and volume force. Surface force and volume force are respectively... so they are bounded... The stress is described by the inner product of a second-order tensor and the normal direction of the surface. The second-order Only three quantities of the stress tensor are independent. Therefore, as long as the stress on three different surfaces of a certain point is known, the stress distribution of this point can be determined... "
Everyone was going crazy. They didn't expect that the detailed explanation of this stress tensor would be so long. A record of breathless concentration.
My hands are about to break.
For the next half hour, Li Zhen began to give examples to explain the theorems.
Then began to explain fluid mechanics.
"Fluid mechanics includes both the basic theories of natural science and the application of engineering and technical science. From the perspective of fluid forces, it can be divided into hydrostatics, fluid kinematics and fluid dynamics; from the perspective of different "mechanical models" "In terms of research, there are ideal fluid dynamics, viscous fluid dynamics, incompressible fluid dynamics, compressible fluid dynamics, etc..."
"There are many branches of fluid mechanics. Let's focus on recording them. Fluid mechanics covers: hydrodynamics, pneumatics, permeability mechanics, explosion mechanics, environmental fluid mechanics, biological rheology..."
"Let's briefly talk about the concepts of these branches, starting with biorheology..."
“…”
The lecture lasted for almost an hour. Li Zhen looked at the time and said, "Okay, class is over. There is a lot of content today. Let's consolidate it after class. Be sure to absorb all today's content within tomorrow. If you need to memorize it by rote, Wherever you come down, you must memorize it by rote. get out of class is over!"
After saying that, Li Zhen took the triangle ruler and left.
Since these transferred teachers seemed useless, Li Zhen didn't count on them anymore. Should I go to class today to avoid wasting another day
"Thank you Master Li!"
Everyone stood up and bowed.
After Li Zhen left, the entire auditorium exploded.
Liu Jinghong held the notebook in his hand, stood on the table and shouted: "Who the hell understands what biorheology is? I don't understand this."
"There is a key point I don't understand. Why is explosion mechanics included in fluid mechanics? How can the shock wave of an explosion be a fluid? Master Li just said it, but I don't understand it. Who can explain it to me?"
"A notebook with clear handwriting, please change it. Whoever tells me a lesson that I didn't understand before, I will let him copy my handwriting and give him a hundred coins!"
"Who can change with me? Who can tell me about the conservation of mass? I am willing to explain the stress tensor to him."
“…”
Those teachers were completely dumbfounded and completely listened to the scriptures!
They understand what the learning model of Kyushu Academy of Sciences is.
(End of chapter)