Sound Waves That Mimic Gravity

Sound Waves That Mimic Gravity
Sound Waves Imitating Gravity - Hot gas moving in a spherical glass vessel under the influence of an acoustic force similar to gravity exhibits signs of convection. Photographs taken 15, 40, and 140 milliseconds after force is activated use false colors to highlight differences in brightness. The main characteristic is an expanding ring of hot gas. - JP Koulakis et al. [one]

A heated gas can now mimic the gravitational-induced convection found inside a star or massive planet, thanks to a newly discovered acoustic effect. Sometimes a scientific breakthrough comes to light physically. By studying the acoustic effect in high-power light bulbs, the researchers created a device that simulates the gravitational field around planets and stars. The researchers proved that the sound waves inside the bulb produce a force that pulls the gas towards the center of the bulb. The gas is repelled by this gravitational force in convection cycles similar to the motions of liquid on the Sun and major planets. With further developments, the system can study convective behavior that is too difficult for computers to replicate.

In 2017, studies on powerful sulfur lamps showed that sound waves can cause hot gas to condense at the centers of the bulbs. Seth Putterman's acoustic group at UCLA dealt with this unexpected phenomenon. The team investigated the clustering and showed that the acoustic radiation strength could explain it. This force, which occurs when sound waves are scattered from an object such as a small bead, is well known from acoustic levitation research. Putterman and colleagues have shown that in light bulbs, this force acts across the gas, where density changes refocus the sound waves, rather than at the surface of an object where the sound is scattered.

According to team member John Koulakis, “We knew that force acts at a sharp interface between something solid and a gas.” “There is a force in the light bulb, even if there is no sharp interaction.”

While modeling this system, the researchers discovered that, within certain limits, the acoustic strength was related to the gas density; just as the gravitational force in a medium is proportional to the density of the medium. If scientists can create "sonic gravity" in the lab, they can study challenging topics in geology and solar physics using a regulated system. In light of this motivation, the team has now set up an experiment with a spherically symmetrical acoustic force, similar to the gravitational field of a planet or star.

To develop their analog system, Putterman and colleagues used microwaves to heat sulfur gas to 3 °C in the core of a 4000 cm wide spherical glass shell. By modulating this microwave signal, they were able to produce sound waves in a spherically symmetric standing wave pattern. The acoustic force in this experiment is inward, at least for the outer space of the sphere, in accordance with the team's model. Since the gravitational force at the Earth's surface is 1000 times stronger than the gravitational-like acoustic force, acoustic gravity must be the dominant factor driving the movement of the gas.

After the acoustic force is activated, images of the sphere show the complex gas motion. This movement was determined by the researchers to be the convective flow caused by the hot gas in the center. Clusters of hot gas “rise to the surface” forming dazzling plumes, just as on a gaseous giant planet or star. As these clusters approach the outer glass boundary, they lose heat and sink back towards the centre.

With other gravity-like forces such as the dielectrophoretic force developing in intense and fluctuating electric fields, researchers have already created planet-like convection. But the research needed a microgravity environment to describe the effects of these other forces because they are so weak.

In contrast, the acoustic force is sufficient to allow tests to be performed in an onshore laboratory.

The team finds convection in a thermodynamic region, away from planetary or stellar conditions. Such conditions will be difficult to achieve, but the researchers plan to increase the core temperature of the gas, which will enable them to investigate thermodynamic fields that are currently outside the scope of computer simulations. While not on a planetary scale, Putterman says, "this configuration will enable an assessment of the sensitivity at which global convection programs capture several important nonlinear phenomena."

Convection modeler Nick Featherstone of the University of Colorado at Boulder describes the experiment as "pretty fantastic."

According to Featherstone, the new arrangement is a "major step forward" as efforts to explore the formation of solar and terrestrial magnetic fields have been constrained by the experimental difficulties of generating spherically symmetrical gravity. “I predict it will lead to a change in the way we study planets and stars in a laboratory context in the coming years.”

Source: physics.aps.org/articles/v16/10

 

 

Günceleme: 22/01/2023 23:31

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