What is the magnus effect. Application of the magnus effect and its amazing properties

Direction of flow. This is the result of the combined action of such physical phenomena as the Bernoulli effect and the formation of a boundary layer in the medium around the streamlined object.

A rotating object creates a vortex motion in the environment around it. On one side of the object, the direction of the vortex coincides with the direction of the flow around and, accordingly, the velocity of the medium from this side increases. On the other side of the object, the direction of the vortex is opposite to the direction of the flow, and the speed of the medium decreases. Due to this speed difference, a pressure difference arises, which generates a transverse force from the side of the rotating body on which the direction of rotation and the direction of flow are opposite, to the side on which these directions coincide. This phenomenon is often used in sports, see, for example, special shots: top spin, dry leaf in football, or the Hop-Up system in airsoft.

The effect was first described by the German physicist Heinrich Magnus in 1853.

Formula for calculating force

Ideal Fluid

Even if the fluid has no internal friction (viscosity), the lift effect can be calculated.

Let the ball be in the flow of an ideal fluid running on it. Flow velocity at infinity (closer, of course, it is distorted) $\vec(u)_\infty$ . To simulate the rotation of the ball, we introduce the circulation of velocity $\Gamma$ Around him. Based on Bernoulli's law, one can get that full strength, acting in this case on the ball, is equal to:

$\vec(R)=-\rho\vec(\Gamma)\times\vec(u)_\infty$ .

It's clear that:

the total force is perpendicular to the flow, that is, the resistance force of the flow of an ideal fluid on the ball is zero (d'Alembert's paradox)
force, depending on the ratio of circulation directions and flow velocity, is reduced to a lifting or lowering force.

viscous liquid

The following equation describes the necessary quantities to calculate the lift generated by the rotation of a ball in a real fluid.

$(F)=(1\over 2) ( \rho) (V^2AC_l)$ $F$ - lifting force $\rho$ is the density of the liquid. $V$ - speed of the ball relative to the medium $A$ - transverse area of the ball $(C_l)$ - lift coefficient ( English)

The lift coefficient can be determined from plots of experimental data using the Reynolds number and the rotation coefficient ((angular velocity*diameter)/(2*line speed)). For rotation ratios from 0.5 to 4.5, the lift coefficient ranges from 0.2 to 0.6.

Application

Wind turbines

Wind generator "air rotor" is a tethered device that rises with helium to a height of 120 to 300 meters)

Turbosails on ships

Since the 1980s, the Cousteau Alsion has operated with a sophisticated turbosail using the Magnus effect.

Since 2010, the cargo ship E-Ship 1 has been in operation with simpler rotary sails Anton Flettner

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Notes

Literature

L. Prandtl"The Magnus Effect and the Wind Ship." (magazine "Successes physical sciences» issue 1-2. 1925)
L. Prandtl. On the motion of a fluid with very little friction. - 1905.

An excerpt characterizing the Magnus Effect

“Well, I’ve finally redone everything, now I’ll rest,” the prince thought, and left Tikhon to undress himself.
Wincing annoyedly at the effort that had to be made to take off his caftan and trousers, the prince undressed, sank heavily onto the bed, and seemed to be lost in thought, looking contemptuously at his yellow, withered legs. He did not think, but he hesitated before the work ahead of him to raise these legs and move on the bed. “Oh, how hard! Oh, if only as soon as possible, these works would end quickly, and you would let me go! he thought. He made this effort for the twentieth time, pursing his lips, and lay down. But as soon as he lay down, all of a sudden the whole bed moved evenly back and forth under him, as if breathing heavily and pushing. It happened to him almost every night. He opened his eyes that had been closed.
"No rest, damned ones!" he grumbled with anger at someone. “Yes, yes, there was something else important, something very important, I saved myself for the night in bed. Gate valves? No, he talked about it. No, something like that was in the living room. Princess Mary was lying about something. Dessal something - this fool - said. Something in my pocket, I don't remember.
- Silence! What did they talk about at dinner?
- About the prince, Mikhail ...
- Shut up, shut up. The prince slammed his hand on the table. - Yes! I know, a letter from Prince Andrei. Princess Mary was reading. Desal said something about Vitebsk. Now I will read.
He ordered the letter to be taken out of his pocket and a table with lemonade and a vitushka, a wax candle, to be moved to the bed, and, putting on his glasses, he began to read. It was only then, in the stillness of the night, in the faint light from under the green cap, that he, having read the letter, for the first time for a moment understood its meaning.
“The French are in Vitebsk, after four crossings they can be at Smolensk; maybe they're already there."
- Silence! Tikhon jumped up. - No, no, no, no! he shouted.
He hid the letter under the candlestick and closed his eyes. And he imagined the Danube, a bright afternoon, reeds, a Russian camp, and he enters, he, a young general, without a single wrinkle on his face, cheerful, cheerful, ruddy, into the painted tent of Potemkin, and a burning feeling of envy for his favorite, just as strong, as then, worries him. And he recalls all those words that were said then at the first meeting with Potemkin. And he imagines with yellowness in her fat face a short, fat woman - Mother Empress, her smiles, words, when she received him for the first time, kindly, and he recalls her own face on the hearse and the collision with Zubov, which was then with her coffin for the right to approach her hand.
“Oh, hurry back to that time, and so that everything now ends quickly, quickly, so that they leave me alone!”

Bald Mountains, the estate of Prince Nikolai Andreevich Bolkonsky, was sixty miles from Smolensk, behind it, and three miles from the Moscow road.
On the same evening, as the prince gave orders to Alpatych, Desalle, having demanded a meeting with Princess Mary, told her that since the prince was not completely healthy and was not taking any measures for his safety, and according to the letter of Prince Andrei, it was clear that his stay in the Bald Mountains unsafe, he respectfully advises her to write with Alpatych a letter to the head of the province in Smolensk with a request to notify her of the state of affairs and the degree of danger to which the Bald Mountains are exposed. Desalles wrote a letter for Princess Marya to the governor, which she signed, and this letter was given to Alpatych with an order to submit it to the governor and, in case of danger, to return as soon as possible.
Having received all the orders, Alpatych, escorted by his family, in a white downy hat (a princely gift), with a stick, just like the prince, went out to sit in a leather wagon laid by a trio of well-fed savras.
The bell was tied up, and the bells were stuffed with pieces of paper. The prince did not allow anyone to ride in the Bald Mountains with a bell. But Alpatych loved bells and bells on a long journey. The courtiers of Alpatych, the zemstvo, the clerk, the cook - black, white, two old women, a Cossack boy, coachmen and various courtyards saw him off.

Continuing the conversation about hydraulic and aerodynamic effects, it follows Special attention pay attention to the effect named after the famous German scientist Heinrich Magnus, who in 1853 proposed a physical explanation for the curvature of the flight path cannonball caused by its random rotation. The flight of a spinning core is in many ways similar to the flight of a spinning ball in football or tennis. The rotation of the ball in flight creates an aerodynamic force that deflects the ball from a straight flight path. Sir Newton wrote about this amazing aerodynamic effect when commenting on the cut shots in tennis.

Usually, the center of gravity of a cannonball does not coincide with its geometric center, which causes a slight twist of the projectile when fired. An arbitrary position of the center of gravity of the nucleus before the shot led to an equally arbitrary deviation of the trajectory of the flight of the nucleus. Aware of this shortcoming, gunners dipped the cannonballs in mercury and then marked them by their upper buoyancy point. Marked kernels were called calibration.

When firing with calibration cores, it was found that in the case when the core was placed in the gun with the center of gravity shifted downwards, “undershoot” was obtained. If the core was laid with the center of gravity up, then a “flight” was obtained. Accordingly, if the center of gravity was located to the right, during the flight of the projectile deviations to the right were obtained, if the center of gravity of the projectile was left, the deviation was observed to the left. The Prussian gunners had special instructions for firing calibration cannonballs.

In the future, they thought of making cores with a deliberately shifted center of gravity. Such shells were called eccentric, and since 1830 they began to be used in the troops of Prussia and Saxony. By correctly placing the eccentric core in the breech of the gun, it was possible to increase the range of the shot up to one and a half times without changing the position of the barrel. Interestingly, scientists had nothing to do with this artillery innovation.

However, the enlightened 19th century demanded a “scientific explanation” of every incomprehensible phenomenon. And so, the Prussian gunners turned to one of the recognized authorities of the emerging aerodynamics - Heinrich Magnus for an explanation of the curvilinear flight path of a cannonball.

Magnus suggested that the matter was not in the shifted center of gravity of the nucleus, as such. He saw the reason in the rotation of the nucleus. To test his hypothesis, Magnus ran a series of laboratory experiments with forced airflow of a rotating body, which was not a sphere, but cylinders and cones. The aerodynamic force generated on the cylinder acted in the same direction as the force deflecting the rotating core.

Thus, Magnus was the first physicist in the laboratory to visually model and confirm the amazing effect of deflecting a cannonball from a direct flight, surprising everyone. Unfortunately, Magnus did not carry out any quantitative measurements in the course of his aerodynamic experiments, but only recorded the occurrence of a deflecting force and the coincidence of its direction with that which took place in artillery practice.

Strictly speaking, Magnus did not quite accurately model the phenomenon of the flight of a swirling nucleus. In his experiments, a rotating cylinder was forcibly blown by a side jet of air. While, as in real artillery practice, the cannonball flies in still air. In accordance with Bernoulli's theorem, the air pressure in the jet decreases in proportion to the square of its speed. In the case of a body moving in still air, there is no real jet velocity, therefore, a drop in air pressure should not be expected.

In addition, in the experiments of Magnus, the force acting on the cylinder was strictly perpendicular to the oncoming jet. In reality, the rotation of the cylinder or ball also increases the force of drag, which has a significant impact on the trajectory of the projectile.

In other words, Magnus's force does not act strictly perpendicular to the flight path, but at some angle, which Magnus did not investigate.

At the time of Magnus, there was still no idea among physicists about the identity of physical phenomena inherent in the real flight of a solid body and phenomena that occur when the wind runs on a motionless body. Therefore, the pioneers of aerodynamics, carried out their first experiments, dropping models from high altitude, thereby simulating the effect of a real flight. For example, Eiffel actively used his tower in aerodynamic experiments.

And only many years later it suddenly became clear that the aerodynamic forces arising from the interaction of a solid body with a liquid or gas flow are almost identical, both when the flow runs onto a stationary body and when the body moves in a stationary medium. And, although this identity involuntarily called into question Bernoulli's theorem, which is valid for a jet flow with real velocity pressure, none of the aerodynamicists began to dig deeper, since Bernoulli's formula made it possible to equally successfully predict the results of a flow around a body, regardless of what actually moves - a stream or solid.

Ludwig Prandtl in his Göttingen laboratory at the beginning of the 20th century was the first of the scientists to do a serious laboratory study of the Magnus force, with measurements of forces and speeds.

In the first series of experiments, the rotation speed of the cylinder was low, so these experiments did not bring anything new, they only confirmed the qualitative conclusions of Magnus. The most interesting thing began in experiments with blowing a rapidly rotating cylinder, when the circumferential speed of the cylinder surface was several times higher than the speed of the oncoming air flow.

Here, for the first time, an anomalously high value of the deflecting force acting on a rotating cylinder was discovered.

With a five-fold excess of the circumferential speed of rotation over the flow velocity, the aerodynamic force on the rotating cylinder, in terms of a square meter of the cylinder section, turned out to be ten times greater than the aerodynamic force acting on a wing with a good aerodynamic profile.

In other words, the thrust force on a rotating rotor turned out to be an order of magnitude higher than the lift force of an aircraft wing!

The incredibly large aerodynamic force that occurs when flowing around a rotating cylinder, Prandtl tried to explain on the basis of Bernoulli's theorem, according to which the pressure in a liquid or gas flow drops sharply with an increase in flow velocity. However, such an explanation is not very convincing, since numerous aerodynamic experiments clearly proved that the pressure drop on a streamlined surface depends on the relative flow velocity, and not on the flow velocity.

With the opposite rotation of the cylinder relative to the flow, the relative flow velocity increases, therefore, the rarefaction should be maximum. With a passing rotation relative to the flow, the relative flow velocity decreases, therefore, the rarefaction should be minimal.

In reality, everything happens exactly the opposite: in the zone of associated rotation, the vacuum is maximum, and in the zone of counter rotation, the vacuum is minimal.

So due to what is the thrust generated when blowing a rotating cylinder?

When Magnus examined a rotating cylinder without lateral airflow, he noticed that there was a pressure drop near the surface of the cylinder: the flame of a candle placed next to the cylinder was pressed against the surface of the cylinder.

Under the action of inertial forces, the near-wall layer of air tends to break away from the rotating surface, creating a rarefaction in the separation zone.

That is, rarefaction is not a consequence of the jet velocity itself, as Bernoulli's theorem states, but a consequence of the curvilinear trajectory of the jet.

With lateral blowing of the rotor, in the area where the oncoming flow coincides in direction with the movement of the near-wall layer, there is an additional spin-up of the air vortex and, hence, an increase in the depth of rarefaction.

On the contrary, in the zone of oncoming movement of the lateral flow, relative to the near-wall layer, there is a slowdown in the rotation of the vortex and a decrease in the depth of rarefaction. The unequal rarefaction depth across the rotor zones leads to the appearance of the resulting lateral force (Magnus force). However, vacuum is present on the entire surface of the rotor.

Perhaps the most important consequence of Prandtl's experiments is the possibility of using an abnormally large force on a rotating rotor to propel the ship. True, this idea did not come to Prandtl himself, but to his compatriot, engineer Anton Flettner, whom we will talk about separately on the following pages.

Igor Yurievich Kulikov

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Everyone has seen how in football or tennis the ball flies along an incredible trajectory. Why is this happening? I don't remember by school curriculum, what would they tell us about it and we always called it just "twisted". But still, what force makes a flying ball describe zigzags?

Now we all find out...

This effect was discovered by the German physicist Heinrich Magnus in 1853. The essence of the phenomenon is that the ball during rotation creates a vortex movement of air around itself. On one side of the object, the direction of the vortex coincides with the direction of the flow around, and the velocity of the medium from this side increases. On the other side of the object, the direction of the vortex is opposite to the direction of the flow, and the speed of the medium decreases. This speed difference generates a lateral force that changes the flight path. The phenomenon is often used in sports, such as special shots: top spin, dry sheet in football or the Hop-Up system in airsoft.

The Magnus effect is well shown in this video. A basketball thrown from a great height vertically down, which was given rotation, changes its trajectory and flies horizontally for some time.

The Magnus effect has been demonstrated on a dam in Australia. Basketball at first it was simply dropped from it, flew almost straight down and landed at the intended point. Then the ball was thrown from the dam a second time, while slightly twisting it (by the way, football players often encounter the Magnus effect when serving “twisted” balls). In this case, the object behaved unusually. A video demonstrating the physical phenomenon was posted on YouTube hosting, in just a couple of days collecting more than 9 million views and almost 1.5 thousand comments.

Rice. 1 1 — boundary layer

A cylinder moving translationally (non-rotating) with a relative velocity V0 flows around a laminar flow, which is non-vortex (Fig. 1b).

If the cylinder rotates and simultaneously moves forward, then the two flows surrounding it will overlap and create the resulting flow around it (Fig. 1c).

When the cylinder rotates, the fluid also moves. The motion in the boundary layer is vortex; it is composed of potential motion, on which rotation is superimposed. At the top of the cylinder, the direction of flow coincides with the direction of rotation of the cylinder, and at the bottom, it is opposite to it. Particles in the boundary layer on top of the cylinder are accelerated by the flow, which prevents the separation of the boundary layer. From below, the flow slows down the movement in the boundary layer, which contributes to its separation. The detached parts of the boundary layer are carried away by the flow in the form of vortices. As a result, a circulation of velocity occurs around the cylinder in the same direction in which the cylinder rotates. According to Bernoulli's law, the pressure of a fluid on upper part cylinder will be smaller than the bottom. This gives rise to vertical force called lift force. When the direction of rotation of the cylinder is reversed, the lift force also reverses direction.

In the Magnus effect, the force F under is perpendicular to the flow velocity V0. To find the direction of this force, you need to rotate the vector relative to the velocity V0 by 90 ° in the direction opposite to the rotation of the cylinder.

The Magnus effect can be observed in an experiment with a light cylinder rolling down an inclined plane.

Rolling Cylinder Schematic

After rolling down an inclined plane, the center of mass of the cylinder does not move along a parabola, as a material point would move, but along a curve going under the inclined plane.

If we replace the rotating cylinder with a vortex (a rotating liquid column) with intensity J=2Sw , then the Magnus force will be the same. Thus, a force acting on the moving vortex from the side of the surrounding fluid is perpendicular to the relative velocity V0 and directed to the side determined by the above vector rotation rule.

In the Magnus effect, the following are interconnected: the direction and speed of the flow, the direction and angular speed, the direction and the resulting force. Accordingly, force can be measured and used, or flow and angular velocity can be measured.

The dependence of the result on the impact has the following form (Zhukovsky-Kutta formula):

where J is the intensity of movement around the cylinder;

r is the density of the liquid;

V0 - relative flow velocity.

Restrictions on manifestations of the physical effect: providing a laminar flow of liquid (gas) over an object with an upward lifting force.

The effect was first described by the German physicist Heinrich Magnus in 1853.

He studied physics and chemistry for 6 years - first at the University of Berlin, then another year (1828) in Stockholm, in the laboratory of Jons Berzelius, and later in Paris with Gay-Lussac and Tenard. In 1831, Magnus was invited as a lecturer in physics and technology at the University of Berlin, then he was a professor of physics until 1869. In 1840, Magnus was elected a member of the Berlin Academy, since 1854 he was a corresponding member of the St. Petersburg Academy of Sciences.

Magnus worked tirelessly all his life on the most diverse issues of physics and chemistry. While still a student (1825), he published his first work on the spontaneous combustion of metal powders, and in 1828 he discovered the platinum salt (PtCl 2NH3) named after him. In 1827-33 he was mainly engaged in chemistry, then work in the field of physics. Of these, the most famous are studies on the absorption of gases by blood (1837-45), on the expansion of gases from heating (1841-44), on the elasticity of water vapor and aqueous solutions (1844-54), on thermoelectricity (1851), electrolysis (1856) , the induction of currents (1858-61), the thermal conductivity of gases (1860), the polarization of radiant heat (1866-68) and the question of the calorific value of gases (since 1861).

No less famous is Magnus as a teacher; most of the outstanding modern German physicists came out of his laboratory, and some Russian scientists also worked in it.

sources

http://www.effects.ru/science/120/index.htm

http://naked-science.ru/article/video/video-effect-magnusa-v-deistvi

https://ru.wikipedia.org/wiki/%D0%9C%D0%B0%D0%B3%D0%BD%D1%83%D1%81,_%D0%93%D0%B5%D0%BD %D1%80%D0%B8%D1%85_%D0%93%D1%83%D1%81%D1%82%D0%B0%D0%B2

Let's remember some other interesting effects in science: for example, and here or. Let's also remember about The original article is on the website InfoGlaz.rf Link to the article from which this copy is made -

A turbosail is a rotary-type ship propulsion system that generates thrust from wind energy through a physical phenomenon known as the Magnus effect.

A turbosail operates on the basis of a physical process that occurs when a liquid or gas flows around a rotating cylindrical or round body and is known as the Magnus effect. The phenomenon got its name from the name of the Prussian scientist Heinrich Magnus, who described it in 1853.

Imagine a ball or cylinder that rotates in a flow of gas or liquid that surrounds them. In this case, the cylindrical body must rotate along its longitudinal axis. During this process, a force arises, the vector of which is perpendicular to the direction of flow. Why is this happening? On the side of the body where the direction of rotation and the flow vector coincide, the speed of the air or liquid medium increases, and the pressure, in accordance with Bernoulli's law, decreases. On the opposite side of the body, where the vectors of rotation and flow are oppositely directed, the speed of the medium decreases, as it were, slows down, and the pressure increases. The pressure difference arising on opposite sides of a rotating body generates a transverse force. In aerodynamics, it is known as lift, which keeps heavier-than-air craft in flight. In the case of rotor sails, this is a force with a vector perpendicular to the direction of the wind on a rotor-sail installed vertically on the deck and rotating along the longitudinal axis.

Rotating Flettner sails

The described physical phenomenon was used by the German engineer Anton Flettner when creating a new type of marine engine. Its rotor sail looked like rotating cylindrical wind towers. In 1922, the inventor received a patent for his device, and in 1924 the first rotary ship in history, the converted schooner Bukau, left the stocks.
Turbosails "Bukau" were driven by electric motors. On the side where the surface of the rotor rotated towards the wind, in accordance with the Magnus effect, an area of increased pressure was created, and on the opposite side - reduced. As a result, thrust arose, which moved the ship, subject to the presence of a side wind. On top of the rotor-cylinders, Flettner put flat plates for better orientation of air flows around the cylinder. This made it possible to double the driving force. A rotating hollow metal cylinder-rotor, using the Magnus effect to create lateral thrust, was subsequently named after its creator.

Flettner's turbosail proved to be excellent in trials. Unlike a conventional sailboat, a strong side wind only improved the performance of the experimental vessel. Two cylindrical rotors made it possible to better balance the vessel. At the same time, by changing the direction of rotation of the rotors, it was possible to change the movement of the vessel forward or backward. Of course, the most favorable wind direction for creating thrust was strictly perpendicular to the longitudinal axis of the vessel.

Turbosail from Cousteau

Sailboats were built in the 20th century, and are being built in the 21st. Modern sails are made from lighter and stronger synthetic materials, and sailing rigs are quickly folded by electric motors, freeing a person from physical work.

However, the idea of a fundamentally new system that uses wind energy to create ship thrust was in the air. It was picked up by the French explorer and inventor Jacques-Yves Cousteau. As an oceanographer, he was very impressed with the use of wind as a traction - a free, renewable and absolutely environmentally friendly source of energy. In the early 1980s, he began work on the creation of such propulsion systems for a modern ship. He took the Flettner turbosail as a basis, but significantly modernized the system, complicating it, but at the same time increasing its efficiency.

What is the difference between Cousteau's turbosail and Flettner's propellers? Cousteau's design is a vertically mounted hollow metal tube with an aerodynamic profile and acting on the same principle as an aircraft wing. In cross section, the pipe has a drop-shaped or egg-shaped shape. On its sides there are air intake grilles through which air is pumped by means of a system of pumps. And then the Magnus effect comes into play. Air turbulence creates a pressure difference inside and outside the sail. A vacuum is created on one side of the pipe, and a seal is created on the other. As a result, a transverse force arises, which causes the ship to move. In essence, a turbosail is a vertically mounted aerodynamic wing: air flows more slowly on one side of it than on the other, creating a pressure difference and transverse thrust. By a similar principle, lift is created on an airplane. The turbosail is equipped with automatic sensors and is mounted on a computer-controlled turntable. The smart machine positions the rotor according to the wind and sets the air pressure in the system.

Cousteau first tested a prototype of his turbosail in 1981 on the Moulin à Vent catamaran while sailing across the Atlantic Ocean. During the voyage, the catamaran escorted the larger ship of the expedition for safety. The experimental turbosail provided thrust, but less than traditional sails and motors. In addition, by the end of the journey, due to metal fatigue, the welding seams burst under the pressure of the wind, and the structure fell into the water. Nevertheless, the idea itself was confirmed, and Cousteau and his colleagues focused on the development of a larger rotary vessel, the Alsion. It was launched in 1985. Turbosails on it are an addition to the aggregation of two diesel engines and several propellers and allow a third to save fuel consumption. Even 20 years after the death of its creator, Alsion is still on the move and remains the flagship of the Cousteau flotilla.

Turbosail vs sailcloth wings

Even compared to the best modern sails, the rotor turbosail delivers 4 times the thrust ratio. Unlike a sailboat, a strong side wind is not only not terrible for a rotary vessel, but is most beneficial for its progress. It moves well even with a headwind at an angle of 250. At the same time, a ship on traditional sails most of all “loves” a tailwind.

Conclusions and perspectives

Now the exact analogues of the Flettner sails are installed as auxiliary propellers on the German cargo ship E-Ship-1. And also their improved model is used on the Alsion yacht, owned by the Jacques-Yves Cousteau Foundation.
Thus, there are currently two types of propulsion system Turbosail. A conventional rotary sail invented by Flettner at the beginning of the 20th century, and its modernized version by Jacques-Yves Cousteau. In the first model, the resultant force is generated outside the rotating cylinders; in the second more complex version, electric pumps create an air pressure difference inside the hollow pipe.

The first turbosail is capable of propelling the vessel only in a side wind. It is for this reason that Flettner's turbosails have not gained distribution in world shipbuilding. Design feature turbosail from Cousteau allows you to get the driving force regardless of the direction of the wind. A ship equipped with such propellers can sail even against the wind, which is an indisputable advantage over both conventional and rotary sails. But, even despite these advantages, the Cousteau system was also not put into production.

This is not to say that today there are no attempts to implement Flettner's idea. There are a number of amateur projects. In 2010, the third ship with rotor sails in history after Bukau and Alsion was built - a 130-meter German Ro-Lo class truck. Propulsion system The vessel is represented by two pairs of rotating rotors and a diesel coupling in case of calm and to create additional traction. Rotor sails play the role of auxiliary engines: for a ship with a displacement of 10.5 thousand tons, four wind towers on the deck are not enough. However, these devices allow you to save up to 40% of fuel on each flight.
But the Cousteau system is unfairly consigned to oblivion, although the economic feasibility of the project has been proven. To date, Alsion is the only full-fledged ship with this type of propulsion. It seems unclear why the system is not used for commercial purposes, in particular on cargo ships, since it allows saving up to 30% of diesel fuel, i.e. money.

People sometimes say that a baseball doesn't actually arc, that it's just an optical illusion. Baseball players and scientists know this isn't true. A major league pitcher can cause the ball to bounce sideways, down, or up as it travels to home. The trajectory of the serve is determined by the speed and direction of rotation given to the ball by the hand of the server. In accordance with the laws of physics, any body that looks like a baseball moving in the air is subjected to several physical strength, the joint influence of which determines the trajectory of its flight.

The baseball is sewn with red thread, which forms 216 stitches during stitching. When flying a spinning ball, the stitches involve Roundabout Circulation adjacent layer of air. As a result, the incoming air moves faster where its direction coincides with the direction of rotation of the ball. The faster air moves, the less pressure it creates. Therefore, the air pressure on the side of the ball rotating in the direction of the oncoming flow becomes less than on its opposite side, rotating against the flow. Just as atmospheric air masses move in the direction of decreasing pressure, a baseball deviates in the direction of twist, i.e., in the direction from which it is located. side surface with lower pressure. The ball, filed by a major league player, makes about 18 revolutions in half a second of its flight to the "home" and can deviate to the side by almost 45 centimeters.

Rotation and the Magnus effect

As the ball flies, it experiences air resistance. On the side of the ball rotating in the direction of flow, this resistance is less. This imbalance creates a force directed at right angles to the direction of the ball's flight. Known as the Magnus effect, this force is proportional to rotational speed, airspeed, and drag.

"Arc" ball

The server throws an "arc" ball, twisting it with the wrist to make the ball spin. Served by a right-hander, such a ball spins down and to the left (counterclockwise when viewed from above) and as a result flies to the lower right corner of the "house". Since the oncoming airflow moves faster on the side of the ball rotating in the direction of the airflow, the ball is deflected to the left and down.

"Screw" ball

The "screw" ball is thrown with the wrist arching towards the body, and not away from it, as in the case of the "arc" ball. This bending of the wrist gives the ball the opposite direction of rotation from the "arc", and causes the ball to deflect up and to the right. A right-handed "screw" ball flies to the upper right corner of the "house".

"fast" ball

A well-served "fast" ball is not an ordinary direct serve, but one of the types of a special twist. When serving a "fast" ball, the server twists it so that the ball rotates backwards, and as a result, under the influence of the Magnus effect, the ball deviates upward. A "fast" ball flying at a speed of 150 kilometers per hour can deviate upwards by almost 10 centimeters.

Ball spin

The difference between "fast", "arc" and "screw" balls lies in the speed and direction of rotation of the ball. The Magnus effect causes the ball to deflect in the direction of its spin. The ball feeding machine gives them different types twisting by changing the speed of rotation of the two ejector wheels. The server does this by changing his grip on the ball.