Sound Power: Acoustic Levitation
British scientists tm physicists from the University of Bristol have developed an acoustic levitator capable of lifting into the air with a single ultrasound beam and holding objects longer than the wavelength. The authors announced a successful experiment a month ago on the pages of Physical Review Letters. Detailed study data is also published here.
According to physicists, they managed to carry out the experiment, thanks to the creation of an acoustic vortex, which caused a sphere with a diameter of one and a half centimeters to take off and be held above the surface of the radiator. If you do not know, then before the wavelength was a fundamental, fundamental constraint for single-beam acoustic levitators. Earlier, the problem was the creation of a levitator using one ray. To obtain the effect, two sources of ultrasound were used. The topic seemed interesting and meaningful to me. Under the cut in more detail about the acoustic levitation of objects and the study of the British.
Vicky defines acoustic levitation as
This phenomenon has been known since 1934, when it was theoretically proved by L. King, and later in 1961 conclusions about the possibility of the phenomenon were made by L.P. Gorkov.
The essence of the principle on which acoustic levitators work is to create interference of coherent sound waves, which leads to the emergence of local areas of pressure increase. Due to this, the body can be held in one or another area of space, as well as move.
Scientists who deal with acoustic levitation believe in the great future of this phenomenon. Futuristic projects involve lifting and moving various objects, equipping the warehouse management system with levitators, and using them in ports and in manufacturing. However, levitators are still very far from such a mass and size. One of the areas where such devices can manifest themselves in the near future is pharmacological technologies, where there is a need for acoustic levitation to increase the degree of purification of substances.
Early single-beam acoustic levitators were developed by various scientists, including Asier Marzo from Bristol and Brazilian Marco Aurelio Brizzotti Andrade from the University of São Paulo. They were able to achieve levitation of objects with a diameter of no more than 4 millimeters. The maximum size of the objects that such a Levitator was flying into the air should have been less than the length of the standing wave.
This time, the Bristol scientists were able to overcome this fundamental limitation, using a special radiator control algorithm. Thanks to the radiation control system, a hemispherical shape and an accurate calculation of the power of ultrasonic radiation sources, it turned out to create acoustic vortices that can hold a large object. The new spherical levitator combines 192 ultrasound emitters with a frequency of 40 kHz (the wavelength at the NW is 0.87 cm). The emitters are mounted on the inner surface of a sphere with a diameter of 192 mm.
Thanks to the ultrasound signal control algorithm, several vortices are created with the same helicity and different directions. In the zone of their action, local areas of high pressure appear, which hold the object. The maximum diameter of the ball that was lifted into the air by the Bristol apparatus is 1.6 cm, which is almost 2 times longer than the wavelength that the device creates. Also, the device is able to change the speed of rotation of the ball, by changing the direction of the ultrasonic vortexes.
Experiments of scientists have demonstrated that when one of the coordinates is fixed (for example, when an object is on the surface), the levitator of a new design is capable of capturing and rotating objects that are 5-6 times longer than the wavelength. This effect opens up new possibilities for the use of devices with acoustic vortices. It is intended to use them to create centrifuges and laboratory control systems for micro and macro particles.
The successes of the Bristol team (Asier Marzo, Mihai Caleap and Bruce W. Drinkwater) show that it is likely that in the near future acoustic levitators will be used to create laboratory and later industrial equipment.
Perhaps in the foreseeable future, acoustic levitation will be able to replace the magnetic one, which is now actively used to create the original design of various devices, including acoustic systems and vinyl players. It is not excluded that someday humanity will see a powerful acoustic tractor beam (as in Ascendancy), capable of fixing and moving really large objects.
According to physicists, they managed to carry out the experiment, thanks to the creation of an acoustic vortex, which caused a sphere with a diameter of one and a half centimeters to take off and be held above the surface of the radiator. If you do not know, then before the wavelength was a fundamental, fundamental constraint for single-beam acoustic levitators. Earlier, the problem was the creation of a levitator using one ray. To obtain the effect, two sources of ultrasound were used. The topic seemed interesting and meaningful to me. Under the cut in more detail about the acoustic levitation of objects and the study of the British.
A few words about acoustic levitation
Vicky defines acoustic levitation as
“The steady position of a weighty object in a standing acoustic wave.”
This phenomenon has been known since 1934, when it was theoretically proved by L. King, and later in 1961 conclusions about the possibility of the phenomenon were made by L.P. Gorkov.
The essence of the principle on which acoustic levitators work is to create interference of coherent sound waves, which leads to the emergence of local areas of pressure increase. Due to this, the body can be held in one or another area of space, as well as move.
Scientists who deal with acoustic levitation believe in the great future of this phenomenon. Futuristic projects involve lifting and moving various objects, equipping the warehouse management system with levitators, and using them in ports and in manufacturing. However, levitators are still very far from such a mass and size. One of the areas where such devices can manifest themselves in the near future is pharmacological technologies, where there is a need for acoustic levitation to increase the degree of purification of substances.
Lyrical digression
In childhood, in the distant 90s, I used to play the Ascendancy space civilization strategy. It was possible to equip planets in it. tractor beam (capture beam), which was able to attract objects from space. I was surprised when I lived until the invention of a similar, albeit miniature, device.
How size doesn’t matter
Early single-beam acoustic levitators were developed by various scientists, including Asier Marzo from Bristol and Brazilian Marco Aurelio Brizzotti Andrade from the University of São Paulo. They were able to achieve levitation of objects with a diameter of no more than 4 millimeters. The maximum size of the objects that such a Levitator was flying into the air should have been less than the length of the standing wave.
This time, the Bristol scientists were able to overcome this fundamental limitation, using a special radiator control algorithm. Thanks to the radiation control system, a hemispherical shape and an accurate calculation of the power of ultrasonic radiation sources, it turned out to create acoustic vortices that can hold a large object. The new spherical levitator combines 192 ultrasound emitters with a frequency of 40 kHz (the wavelength at the NW is 0.87 cm). The emitters are mounted on the inner surface of a sphere with a diameter of 192 mm.
Thanks to the ultrasound signal control algorithm, several vortices are created with the same helicity and different directions. In the zone of their action, local areas of high pressure appear, which hold the object. The maximum diameter of the ball that was lifted into the air by the Bristol apparatus is 1.6 cm, which is almost 2 times longer than the wavelength that the device creates. Also, the device is able to change the speed of rotation of the ball, by changing the direction of the ultrasonic vortexes.
Unexpected 2D effects
Experiments of scientists have demonstrated that when one of the coordinates is fixed (for example, when an object is on the surface), the levitator of a new design is capable of capturing and rotating objects that are 5-6 times longer than the wavelength. This effect opens up new possibilities for the use of devices with acoustic vortices. It is intended to use them to create centrifuges and laboratory control systems for micro and macro particles.
Total
The successes of the Bristol team (Asier Marzo, Mihai Caleap and Bruce W. Drinkwater) show that it is likely that in the near future acoustic levitators will be used to create laboratory and later industrial equipment.
Perhaps in the foreseeable future, acoustic levitation will be able to replace the magnetic one, which is now actively used to create the original design of various devices, including acoustic systems and vinyl players. It is not excluded that someday humanity will see a powerful acoustic tractor beam (as in Ascendancy), capable of fixing and moving really large objects.
Source: https://habr.com/ru/post/410567/