Strange changes in the trajectory of the ball for the layman seem like a miracle. But for professional football players, basketball players, billiards players, such tricks are an indicator of skill. And here we recall the laws of physics, which throws up gifts such as the Magnus effect. Initially seen in aerodynamics, today this law of changing the trajectory of a spherical object has found very wide application. More recently, a video appeared on the Internet that clearly demonstrated this physical phenomenon by the example of a basketball. The video collected more than 9 million views in two days and fueled interest in the Magnus effect and its incredible applications.
Background
It all started with the fact that the Prussian gunners could not understand why the nuclei from their guns constantly fall into the wrong direction. The rotation of the nucleus in flight with its center of gravity that does not coincide with the geometric one curved the flight path. Isaac Newton wrote about the aerodynamic force affecting the flight of a rotating ball, and the Prussian commanders turned to the famous German scientist Heinrich Gustav Magnus (1802-1870) for an explanation of the curved paths of the core, which in 1853 gave a scientific explanation for this phenomenon.
The scientist suggested that it was not at all the center of gravity of the object, but its rotation. He conducted a series of experiments, and although he did not make any mathematical calculations, he holds the primacy of proof of the aerodynamic force that changes the flight path of a rotating body.
After Magnus, Ludwig Prandtl (1875-1953) became interested in this force, who measured strength and speed. Its most important achievement is the establishment of the possibility of using the arising force on a rotating rotor (cylinder) to ensure translational motion. But in practice, another German already realized this idea - engineer Anton Flettner (1885-1961). About rotary sails of Flettner and Cousteau a bit later.
The explanation is not for physicists
Given the laws of Newtonian physics of solids, in simple words, the process is as follows. A swirling round object is gaining speed, the air in front of the object moves in the direction of its rotation and stretches along and towards the center. On the other side of the object, the air moves in the opposite direction with respect to the direction of rotation. As a result, the flow moves away and the object displaces the air on one side, and the air on the other hand forms a response force, but in the other direction, which changes the flight path of the object. The process diagram is shown in the figure above, this is the notorious Magnus effect.
Flettner's Windship
Anton Flettner received the German patent for a rotary vessel on September 16, 1922. And already in October 1926, a real sensation in the Kiel Bay produced an unusual vessel with two large pipes on board and an openwork mast. It was the first Buckau rotary vessel to descend from the slipways of the Friedrich Krupp shipbuilding company.
Flettner used the Magnus effect and the force generated by the flow around rotating cylinders and directed perpendicular to the direction of flow. From the side where the direction of the vortex flow created by the rotating body coincides with the direction of the air flow, the force and speed of movement increase sharply. It was these rotors that would later be called his name that the young engineer Flettner replaced the sails.
The rotors of this ship rotated from electric motors. Where the rotor rotated towards the wind, an area with increased pressure was created. On the opposite side - with reduced. The resulting force moved the ship.
Buckau passed the test with flying colors. In 1925 he sailed from Danzig to Scotland under weather conditions, when sailing ships did not dare to go to sea. The campaign was successful, and the crew of the ship was reduced to 10 people, against 20 on a sailboat.
Forced Oblivion
A bright future opened before the Flettner rotors. The success of the project was confirmed by the vessel of the Hamburg company Barbara. It was a cargo liner, the movement of which was provided by three 17-meter rotors, which set a speed of 13 knots with a wind of 4-6 points.
Despite the apparent success of the project, they forgot about it for a long time. And there are several reasons for this. Flettner himself lost interest in shipping and became interested in aviation, the time of the Great Depression of the 1920s came.
Resuscitation of ships with rotor units
The continuation of the rotary vessel Flettner herds turboparus Jacques-Yves Cousteau. A famous researcher and fighter for environmentally friendly vehicles in April 1885 launched the Alkiona vessel, equipped with patented turbo-sails, in which the Magnus effect was used. This ship is still underway today.
Unfortunately, Cousteau’s followers were not very interested in rotary installations on ships, and interest in them faded again. They were remembered with the onset of the oil crisis, and in 2010 a third vessel with rotary units was launched. This is a heavy 130 meter Enercon E-Ship 1 with four Flettner rotors. Today it is engaged in the transportation of wind turbines from Germany to Europe, can withstand up to 9 tons of cargo and has a speed of 17 knots. The crew is only 15 people.
Ship companies Wind Again (Singapore), Wartsila (Finland) and some others became interested in rotary installations. Oil scarcity and alarming global warming appear to play a role in bringing windmills back to modern ships.
Application in the aircraft industry
The application of the Magnus effect in aviation was implemented in various design solutions. In the simplest forms, wing-shaped wings rotating during flight were used. Among the founders of this trend was the Austrian inventor Karl Gligorin, who proposed installing a fairing on the rotor that repeats the shape of the wing. In Amsterdam, E.B. worked on similar projects. Wolf, Americans John D. Gerst and C. Popper in 1932 even tested their plane with wing-shaped wings.
The North American-Rockwell model YOU-10A Bronco turned out to be efficient, re-equipped with rotating shafts in 1964. It was a project by a professor from Peru, Alberto Alvarez-Calderona. However, the prototype had more disadvantages than advantages.
Despite the efforts, the Magnus effect in aviation did not take root. The practical use of rotor-type wings is associated with a number of problems and so far has not justified itself economically.
Magnus effect and wind generators
The development of the alternative energy industry is especially relevant in our time. And in this industry, the Magnus effect has been applied. Rotary blades come to replace rotary wind generators, which are most effective at frequent and low wind speeds of 2-6 m / s. They have basically an axis around which the cylinders rotate. The first such installation manufactured by Aerolla appeared near Minsk (Belarus) in 2015. Its power was 100 kW, the diameter of the turbine rotor 36 meters. It works at an estimated wind speed of 9.5 m / s.
Work in this direction continues at the Novosibirsk Institute of Applied Mechanics SB RAS, and there are already prototypes of wind generators that use the Magnus effect with a power of up to 2 MW.
Not quite familiar application
This effect of changing the trajectory of the ball is widely used in sports: top-spin and “dry sheet” kicks in football, the Hop Up system in airsoft.
The Magnus effect is now widely used in the design of aircraft models. For example, an airplane made of cardboard, an electric motor, and paper cups for fast food was designed by PeterSripol.
The Magnus effect is used in the manufacture of kites. For example, a snake in the form of a turntable by designer D. Edwards or S. Albertson.
But for "hurricane hunters" this physical phenomenon can become very dangerous. If the bottom between the car and the ground is not well closed, then through the gap a hurricane wind can create a huge lifting force that will easily lift the car into the air.