How do airplanes fly?

In the middle ages, in 1738, a man named Daniel Bernoulli wrote a book called Hydrodynamics. In his book he mentioned a principle about fluids.

He said that if the velocity of a fluid increases, the static pressure of the medium decreases, this is the principle, in a sense, the potential energy of the fluid turns into kinetic energy.

You may ask what this means. Let me try to explain:

Let's say a fluid flows through a horizontal pipe. Why a horizontal pipe, why not a vertical one? Because we don't want to consider the weight effect of the fluid. I'm talking about something like the pool equation, suppose there is a pipe connected to a large reservoir. Let's say our reservoir is so big that the water flowing through the pipe cannot reduce the height of the water in the reservoir so quickly. So our assumption is that the pressure inside the pipe doesn't change, the pressure is constant.

The fluid flowing through this pipe, let's choose water as our fluid in this example, exerts a pressure on the walls of the pipe as it flows through the pipe. If it is a rubber hose, for example, this horizontal pipe, we notice that the rubber hose is bulging as water flows through it.

Anyone who has watered a garden has noticed this. The hose connected to the fountain bulges as we water the lawn. So the water flowing through it has a certain pressure, and the pressure causes the hose to bulge.

Bernoulli says that if we reduce the cross-section of the hose in a certain place, the amount of water flowing through it does not change, only in this reduced cross-section the fluid accelerates and the pressure on the walls decreases in this part of the hose. You are going to water a little further away in the garden and the hose is not enough. So you add a hose with a smaller cross-section. The amount of water flowing does not change, but the pressure exerted on the hose by the water in the narrower section is less. The water flowing through the hose in this section also flows faster. If the cross-section of the hose is enlarged again as in the first part, the pressure increases again and the speed decreases.

It sounds like the pressure and the speed of the water have nothing to do with each other, but Daniel Bernoulli discovered this in his experiments.

We actually do something similar with our hands when we water flowers, we squeeze the end of the hose a little bit to squirt the water farther. So we actually reduce the cross-section of the hose. This increases the speed of the water and allows the water to reach farther points.

Bernoulli studied this simple subject in his time and put it into some formulas.

Today, we can fly huge airplanes in the sky because we can calculate this pressure change with the right formulas. Bernoulli established the principles of calculation in his time. There were no airplanes in his time, but the principle he found was used in the wing designs of airplanes years later. It is still in use today.

Airplane wings are designed so that the speed of the air flowing over the wing is faster than the air flowing under the wing. In other words, the pressure force exerted by the air on the wing surfaces from below is greater than the pressure force exerted from above. In this case, the airplane is pushed upwards due to the difference between the pressure forces. This is the force that pushes the airplane upwards on take-off. It is this force that keeps it hovering during flight.

With the same principles, our water meters work, our gas meters work. Many more devices working on the basis of this principle have been produced.

Pressure differences are measured in pipes of different cross-sections with a reduced pipe cross-section inside the meter, and since the pipe diameters are known, the speed difference of the fluid passing through it is calculated. Based on this difference, the amount of fluid passing through the formula is calculated.

The same principle is used in car engines and golf balls.

The dimples on the surface of golf balls are the secret to throwing the ball much farther. If you hit the same shot with a ball of the same size and weight without dimples on the surface, the ball will not travel as far.

Those who have orchards know that the sprayers we use to spray trees work on the same principle, as do the paint sprayers used by car painters.

There are many scientists like Daniel Bernoulli who have touched our lives. We often don't realize the benefits of their work, but believe me, life would be much more difficult without these people. All the needs of the modern world have been produced by the work of scientists. 

Today Daniel Bernoulli came to my mind for some reason, I wanted to share a couple of examples of how a simple principle discovered by this Swiss scientist has touched our lives. There are many more works of Daniel Bernoulli, but I think even this simple discovery is enough for us to remember him with respect.

There are many more scientists who have touched our lives, some of them perhaps spent their lives for nothing. There are those who lost their health and died because of their work. But still, what they did for science and their efforts are enough to be remembered with respect, because they all tried to benefit humanity.

I wanted to share with you a little bit about science these days, because I am not happy with the recent developments in our country. Festivals are being canceled, artists are being jailed for no reason. There is constant news of violence against women every day, constant bans, constant poverty and corruption. The state of the economy is obvious. 

I sense a hatred in the tongues of some commentators on the screens. Especially the commentators we think of as smart and well-behaved. They still talk about how conservative people were once oppressed. It is as if we have lived in different worlds all these years. As if dreams of a life together do not exist in the minds of such people. As if they were the only ones who were oppressed. As if they are the only ones who have suffered in this country. You can feel the hatred they have accumulated for years in their language, in the way they speak. This language of hatred is also the constant language of those at the top. I feel very sad for the situation the country has been brought to.

Today we have the power, now it is our day and now you should experience the same oppression, they make comments with a language of hate on the screens for every daily event.

I think they are on the wrong track and I hope one day they will realize their wrong thinking.

I don't know, maybe it is about voter consolidation again. Maybe these issues are being deliberately inflated again. But it doesn't matter why. After all, I don't like what is being done.

My intention is to shed some light on the services that people who have not accumulated such hatreds throughout history, namely scientists, have done and are doing for humanity, and to shed some light on what we need to do. Unfortunately, we have not contributed much to human history in terms of science. Maybe our future generations will be more successful in these matters.

All of these scientists I have mentioned have their own world of beliefs, maybe they have experienced pressures throughout their lives, some of them may have lost their lives for saying what they know is right, but it doesn't matter what they have gone through or their world of beliefs, I think what they have done is just a service to humanity and they all deserve respect.

Again I say stay with science, science is the right path and the rest is nothing else.

Love and respect to everyone from Moscow.