Magnus effect and turbosail

2024 Author: Seth Attwood | [email protected]. Last modified: 2024-01-10 19:46

In Australia, amateur physicists have demonstrated the Magnus effect in action. The experiment video, posted on YouTube hosting, has received over 9 million views.

The Magnus effect is a physical phenomenon that occurs when a stream of liquid or gas flows around a rotating body. When a flying round body rotates around it, nearby air layers begin to circulate. As a result, in flight, the body changes its direction of motion.

For the experiment, amateur physicists chose a dam 126.5 meters high and an ordinary basketball. At first, the ball was simply thrown down, it flew parallel to the dam and landed at the marked point. The second time, the ball was dropped, slightly scrolling around its axis. The flying ball flew along an unusual trajectory, clearly demonstrating the Magnus effect.

The Magnus Effect explains why in some sports, such as soccer, the ball flies in a strange trajectory. The most striking example of the "abnormal" flight of the ball can be seen after a free kick by football player Roberto Carlos during the June 3, 1997 match between the national teams of Brazil and France.

The ship is under turbo sails

The famous documentary series "The Cousteau Team's Underwater Odyssey" was shot by the great French oceanographer in the 1960s – 1970s. The main ship of the Cousteau was then converted from the British minesweeper "Calypso". But in one of the subsequent films - "Rediscovery of the World" - another ship appeared, the yacht "Alcyone".

Looking at her, many viewers asked themselves the question: what are these strange pipes installed on the yacht?.. Maybe they are pipes of boilers or propulsion systems? Imagine your amazement if you find out that these are SAILS … turbosails …

The Cousteau fund acquired the yacht "Alkion" in 1985, and this ship was considered not so much as a research ship, but as a base for studying the efficiency of turbosails - the original ship propulsion system. And when, 11 years later, the legendary "Calypso" sank, "Alkiona" took her place as the main vessel of the expedition (by the way, today "Calypso" is raised and is in a semi-plundered state in the port of Concarneau).

Actually, the turbosail was invented by Cousteau. As well as scuba gear, an underwater saucer and many other devices for exploring the depths of the sea and the surface of the oceans. The idea was born in the early 1980s and was to create the most environmentally friendly, but at the same time convenient and modern propulsion system for a waterfowl. The use of wind power seemed to be the most promising area of research. But here's the bad luck: mankind invented a sail several thousand years ago, and what could be simpler and more logical?

Of course, Cousteau and his company understood that it was impossible to build a ship powered exclusively by sail. More precisely, perhaps, but its driving performance will be very mediocre and dependent on the vagaries of the weather and wind direction. Therefore, it was originally planned that the new "sail" will only be an auxiliary force, applicable to help conventional diesel engines. At the same time, a turbosail would significantly reduce diesel fuel consumption, and in a strong wind it could become the only propulsion of the vessel. And the look of the research team turned to the past - to the invention of the German engineer Anton Flettner, the famous aircraft designer who made a significant contribution to shipbuilding.

Flettner's rotor and the Magnus effect

On September 16, 1922, Anton Flettner received a German patent for the so-called rotary vessel. And in October 1924, the experimental rotary vessel Buckau left the stocks of the shipbuilding company Friedrich Krupp in Kiel. True, the schooner was not built from scratch: before the installation of Flettner's rotors, it was an ordinary sailing vessel.

Flettner's idea was to use the so-called Magnus effect, the essence of which is as follows: when an air (or liquid) stream flows around a rotating body, a force is generated that is perpendicular to the direction of the flow and acts on the body. The fact is that a rotating object creates a vortex motion around itself. On the side of the object, where the direction of the vortex coincides with the direction of the flow of liquid or gas, the velocity of the medium increases, and on the opposite side, it decreases. The difference in pressure and creates a shear force directed from the side where the direction of rotation and the direction of flow are opposite to the side where they coincide.

This effect was discovered in 1852 by the Berlin physicist Heinrich Magnus.

Magnus effect

German aeronautical engineer and inventor Anton Flettner (1885-1961) went down in the history of navigation as a man trying to replace sails. He had a chance to travel for a long time on a sailing ship across the Atlantic and Indian oceans. Many sails were set on the masts of sailing ships of that era. Sailing equipment was expensive, complex, and aerodynamically not very efficient. Constant dangers lurked sailors who, even during a storm, had to sail at 40-50 meters height.

During the voyage, the young engineer had the idea to replace the sails, which require more effort, with a simpler but effective device, the main propulsion of which would also be the wind. Pondering this, he recalled aerodynamic experiments conducted by his compatriot physicist Heinrich Gustav Magnus (1802-1870). They found that when a cylinder rotates in an air flow, a transverse force arises with a direction depending on the direction of rotation of the cylinder (Magnus effect).

One of his classic experiments looked like this: “A brass cylinder could rotate between two points; the rapid rotation of the cylinder was imparted, as in a top, by a cord.

The rotating cylinder was placed in a frame, which, in turn, could easily be rotated. A strong jet of air was sent to this system using a small centrifugal pump. The cylinder deviated in a direction perpendicular to the air stream and to the cylinder axis, moreover, in the direction from which the directions of rotation and the jet were the same "(L. Prandtl" The Magnus Effect and the Wind Ship ", 1925).

A. Flettner immediately thought that the sails could be replaced by rotating cylinders installed on the ship.

It turns out that where the surface of the cylinder moves against the air flow, the wind speed decreases and the pressure increases. On the other side of the cylinder, the opposite is true - the speed of the air flow increases, and the pressure decreases. This difference in pressure from different sides of the cylinder is the driving force that makes the vessel move. This is the basic principle of operation of rotary equipment, which uses the force of the wind to move the vessel. Everything is very simple, but only A. Flettner "did not pass by", although the Magnus effect has been known for more than half a century.

He began to implement the plan in 1923 on a lake near Berlin. Actually, Flettner did a pretty simple thing. He installed a paper cylinder-rotor about a meter in height and 15 cm in diameter on a meter-long test boat, and adapted a clock mechanism to rotate it. And the boat sailed away.

The captains of sailing ships scoffed at A. Flettner's cylinders, with which he wanted to replace the sails. The inventor managed to interest wealthy patrons of art with his invention. In 1924, instead of three masts, two rotor cylinders were installed on the 54-meter schooner "Buckau". These cylinders were powered by a 45 hp diesel generator.

The Bucau's rotors were powered by electric motors. Actually, there was no difference from the classical experiments of Magnus in the design. On the side where the rotor rotated against the wind, an area of increased pressure was created, on the opposite side, a low pressure area. The resulting force is what propelled the ship. Moreover, this force was about 50 times greater than the force of wind pressure on a stationary rotor!

This opened up great prospects for Flettner. Among other things, the rotor area and its mass were several times less than the area of the sail rig, which would have given equal driving force. The rotor was much easier to control, and it was quite cheap to manufacture. From above, Flettner covered the rotors with plate-planes - this increased the driving force by about two times due to the correct orientation of the air flows relative to the rotor. The optimal height and diameter of the rotor for "Bukau" was calculated by blowing a model of the future ship in a wind tunnel.

Flettner's rotor proved to be excellent. Unlike an ordinary sailing vessel, a rotary ship was practically not afraid of bad weather and strong side winds, it could easily sail with alternating tacks at an angle of 25º to the headwind (for a normal sail, the limit is about 45º). Two cylindrical rotors (height 13.1 m, diameter 1.5 m) made it possible to perfectly balance the vessel - it turned out to be more stable than the sailboat that Bukau was before the restructuring.

The tests were carried out in calm weather, and in a storm, and with deliberate overload - and no serious shortcomings were identified. The most advantageous for the movement of the vessel was the direction of the wind exactly perpendicular to the axis of the vessel, and the direction of movement (forward or backward) was determined by the direction of rotation of the rotors.

In mid-February 1925, the schooner Buckau, equipped with Flettner's rotors instead of sails, left Danzig (now Gdansk) for Scotland. The weather was bad and most of the sailboats did not dare to leave the ports. In the North Sea, the Buckau had to deal seriously with strong winds and large waves, but the schooner heeled aboard less than other sailboats encountered.

During this voyage, it was not necessary to call on the deck of the crew members to change sails depending on the strength or direction of the wind. One navigator of the watch was enough, who, without leaving the wheelhouse, could control the activity of the rotors. Previously, the crew of a three-masted schooner consisted of at least 20 sailors, after its conversion into a rotary ship, 10 people were enough.

In the same year, the shipyard laid the foundation for the second rotary ship - the mighty cargo liner "Barbara", propelled by three 17-meter rotors. At the same time, one small motor with a capacity of only 35 hp was enough for each rotor. (at the maximum rotation speed of each rotor 160 rpm)! The rotor thrust was equivalent to that of a propeller driven propeller coupled with a conventional ship diesel engine with a capacity of about 1000 hp. However, the ship also had a diesel engine: in addition to the rotors, it set in motion the propeller (which remained the only propulsion device in case of calm weather).

Promising experiments prompted the shipping company Rob. M. Sloman from Hamburg to build the ship Barbara in 1926. It was planned in advance to equip turbosails - Flettner's rotors. On a vessel 90 m long and 13 m wide, three rotors with a height of about 17 m were mounted.

Barbara has been successfully transporting fruit from Italy to Hamburg for some time, as planned. Approximately 30–40% of the voyage time the vessel was sailing due to the force of the wind. With a wind of 4-6 points "Barbara" developed a speed of 13 knots.

It was planned to test the rotary vessel on longer voyages in the Atlantic Ocean.

But in the late 1920s, the Great Depression struck. In 1929 the charter company abandoned the further lease of the Barbara and was sold. The new owner removed the rotors and refitted the ship according to the traditional scheme. Still, the rotor lost to the screw propellers in combination with a conventional diesel power plant due to its dependence on the wind and certain limitations in power and speed. Flettner turned to more advanced research, and Baden-Baden eventually sank during a storm in the Caribbean in 1931. And they forgot about rotary sails for a long time …

The beginning of rotary vessels, it would seem, was quite successful, but they did not receive development and were forgotten for a long time. Why? First, the "father" of rotary vessels A. Flettner plunged into the creation of helicopters and ceased to be interested in sea transport. Secondly, despite all their advantages, rotary vessels have remained sailing ships with their inherent disadvantages, the main of which is dependence on the wind.

Flettner's rotors were again interested in the 80s of the twentieth century, when scientists began to propose various measures to mitigate climate warming, reduce pollution, and more rational use of fuel. One of the first to recall them was the French explorer Jacques-Yves Cousteau (1910–1997). To test the operation of the turbosail system and reduce fuel consumption, the two-masted catamaran "Alcyone" (Alcyone is the daughter of the god of the winds Aeolus) was converted into a rotary vessel. Having set out on a sea voyage in 1985, he traveled to Canada and America, circled Cape Horn, bypassed Australia and Indonesia, Madagascar and South Africa. He was transferred to the Caspian Sea, where he sailed for three months, doing various research. Alcyone still uses two different propulsion systems - two diesel engines and two turbosails.

Turbo sail Cousteau

Sailboats were built throughout the 20th century. In modern ships of this type, sailing armament is folded with the help of electric motors, new materials make it possible to significantly lighten the structure. But a sailboat is a sailboat, and the idea of using wind energy in a radically new way has been in the air since the days of Flettner. And she was picked up by the tireless adventurer and explorer Jacques-Yves Cousteau.

On December 23, 1986, after the Alcyone, mentioned at the beginning of the article, was launched, Cousteau and his colleagues Lucien Malavar and Bertrand Charier received joint patent No. US4630997 for "a device that creates force through the use of a moving liquid or gas." The general description reads as follows: “The device is placed in an environment moving in a certain direction; in this case, a force arises that acts in a direction perpendicular to the first. The device avoids the use of massive sails, in which the driving force is proportional to the sail area. " What is the difference between Cousteau's turbosail and Flettner's rotary sail?

In cross-section, a turbosail is something like an elongated drop rounded from the sharp end. On the sides of the "drop" there are air intake grilles, through one of which (depending on the need to move forward or backward) air is sucked out. For the most efficient wind suction, a small fan driven by an electric motor is installed into the air intake on the turbo sail.

It artificially increases the speed of air movement from the leeward side of the sail, sucking in the air stream at the moment of its separation from the plane of the turbo-sail. This creates a vacuum on one side of the turbosail while preventing the formation of turbulent vortices. And then the Magnus effect acts: rarefaction on one side, as a result - a transverse force capable of setting the ship in motion. Actually, a turbosail is a vertically positioned aircraft wing, at least the principle of creating a propulsive force is similar to the principle of creating a lift of an aircraft. To ensure that the turbosail is always turned to the wind in the most advantageous direction, it is equipped with special sensors and is installed on a turntable. By the way, Cousteau's patent implies that air can be sucked out from the inside of a turbo-sail not only by a fan, but also, for example, by an air pump - thus Cousteau closed the gate for subsequent “inventors”.

Actually, for the first time, Cousteau tested a prototype turbosail on the Moulin à Vent catamaran in 1981. The largest successful sailing of the catamaran was a trip from Tangier (Morocco) to New York under the supervision of a larger expedition ship.

And in April 1985, in the port of La Rochelle, the Alcyone, the first full-fledged ship equipped with turbosails, was launched. Now she is still on the move and today is the flagship (and, in fact, the only large ship) of the Cousteau flotilla. The turbo sails on it are not the only mover, but they help the usual coupling of two diesels and

several screws (which, by the way, reduces fuel consumption by about a third). If the great oceanographer were alive, he probably would have built several more similar ships, but the enthusiasm of his associates after the departure of Cousteau noticeably diminished.

Shortly before his death in 1997, Cousteau was actively working on the project of the ship "Calypso II" with a turbosail, but did not manage to complete it. According to the latest data, in the winter of 2011, "Alkiona" was in the port of Caen and was waiting for a new expedition.

And again Flettner

Today, attempts are being made to revive Flettner's idea and make rotary sails mainstream. For example, the famous Hamburg company Blohm + Voss, after the 1973 oil crisis, began active development of a rotary tanker, but by 1986, economic factors covered up this project. Then there was a whole series of amateur designs.

In 2007, students at the University of Flensburg built a catamaran powered by a rotary sail (Uni-cat Flensburg).

In 2010, the third ever ship with rotary sails appeared - the heavy truck E-Ship 1, which was built by order of Enercon, one of the largest manufacturers of wind turbines in the world. On July 6, 2010, the ship was first launched and made a short voyage from Emden to Bremerhaven. And already in August, he went on his first working trip to Ireland with a load of nine wind turbines. The vessel is equipped with four Flettner rotors and, of course, a traditional propulsion system in case of calm and for additional power. Still, rotary sails serve only as auxiliary propellers: for a 130-meter truck, their power is not enough to develop the proper speed. The engines are nine Mitsubishi power plants, and the rotors are powered by a Siemens steam turbine that uses energy from exhaust gases. Rotary sails provide 30 to 40% fuel savings at 16 knots.

But Cousteau's turbosail still remains in some oblivion: "Alcyone" today is the only full-size ship with this type of propulsion. The experience of German shipbuilders will show whether it makes sense to further develop the theme of sails operating on the Magnus effect. The main thing is to find a business case for this and prove its effectiveness. And there, you see, all world shipping will move to the principle that a talented German scientist described more than 150 years ago.

On August 2, 2010, the world's largest manufacturer of wind power plants Enercon launched a 130-meter rotary vessel, 22 m wide, which was later named “E-Ship 1”, at the Lindenau shipyard in Kiel. Then it was successfully tested in the North and Mediterranean Seas, and is currently transporting wind generators from Germany, where they are produced, to other European countries. It develops a speed of 17 knots (32 km / h), simultaneously transports more than 9 thousand tons of cargo, its crew is 15 people.

Singapore-based shipping company Wind Again, a fuel and emission reduction technology, offers specially designed Flettner rotors (foldable) for tankers and cargo ships. They will reduce fuel consumption by 30-40% and will pay off in 3-5 years.

The Finnish marine engineering company Wartsila is already planning to adapt turbosails on cruise ferries. This is due to the desire of the Finnish ferry operator Viking Line to reduce fuel consumption and environmental pollution.

The use of Flettner rotors on pleasure craft is being studied by the University of Flensburg (Germany). Rising oil prices and alarming climate warming appear to be favorable conditions for the return of wind turbines.