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Jump rope in a cookie jar



HZDR scientist discovers the phenomenon of liquid metal phenomenon

Then, anyone who spills a liquid always starts turbulence: the hot fluid grows and it is mixed with cold waste. In some cases, several vortices could be combined to create a larger structure, a high-speed circulation. Collaborating at the Los Angeles University of California (UCLA), along with Tobias Vogt (The latest news from Dresdner: "Helmholtz-Zentrum Dresden-Rossendorf (HZDR) Surprisingly: In experiments, this structure moved very similar to selling the rope. The result can help to better understand certain phenomena on the surface of the sun.

Experiments with Galia liquid, Dresden and California researchers have demonstrated that the circulation called high-circulation moves to mopeds. – Picture © HZDR, T. Vogt

This is particularly noticeable in a lava lamp: when its liquid is heated, the bubbles rise and lower. Experts refer to this phenomenon at the same temperature as convection. According to certain conditions, thermal turbulence converges and complements the super-structured structure and the large-scale circulation.

An example of this can be found in the cloud sky. If the wind is blowing from a given direction, several centimeters of clouds can be more than ten kilometers in length – creating a cloud path. You can also see the phenomenon of the sun: If you look at the surface through a special telescope, the grains accumulate a lot. This "granulation" comes from convection: the lower part, the heat and bright material rises to the surface where it cools and a specimen is formed as dark material. The granules are 1,000 kilometers long and only a few minutes away.

"So far, experts believe that large-scale circulation is bi-dimensional," he explains Tobias Vogt, from the HZDR Fluid Dynamics Institute. "However, our experiment today questions this idea." The starting point was a trip that Vogt won in 2016 together with the Helmholtz Ph.D. She took her three months to UCLA. Together with local experts in the field, Planetary and Science Sciences, he designed a test setup to investigate the most important traffic.

The core of the experiment was the cylindrical container, the size of a cookie filled liquid liquid galley, with a metal of less than 30 degrees. "It's very hot and it's three times thinner than water," said Tobias Vogt. "Convection phenomena are so evident." At the bottom of the container, when it is heated to 70 degrees centimeters, the lid can cool down around 30 centimeters. As a result of this difference in temperature, liquid metal began to stir: hot fluid rose and turbulence was formed everywhere.

Turbulence like giants

To observe the event, the team had to use a special ultrasound technique: "Galion is not transparent, laser procedures were not a question," says Vogtek. "Instead, we use a procedure by the doctors, in principle, to display bleeding in ships." Specifically, researchers sent short ultrasonic pulses to the container. Depending on the flow velocity, the pulses were reflected differently, measured with the sensors. Three-dimensional flow profiles were mixed with liquid metals, combined with numerical simulators in a supercomputer.

Jumping Rope Swirls: (A) 3D projective visualization of stream currents in a climate-fired tank. It surrounds the rope that sells the stream, the color of rationality that indicates the local speed. In addition, the color of the central sheet color indicates velocity, and the linear velocities can be seen through the integral linear combination (LIC – line-integral convolución technique). Jump rope cycle shows B, C, D and E. Cross section cross sections are shown. The core of the high-traffic circulation core (LSC) has a minimum speed (pink). BN, LSC is limited to half. Cn came out of the middle flight. The highest speeds of C / E (green) also show a clear upward and downward stream. Source: pnas.org/content/early/2018/11/21/1812260115

In every profile, large-scale circles were clearly identified – they recall a stream snake. "To our surprise, we found that this structure is similar to the store," explained Vogt. "Continuous circulation, movement and large-scale circulation structure are in three dimensions". This clarifies the doubts about the common theoretical explanations, which is to treat it as a two-dimensional phenomenon and now it is necessary to analyze it.

In the end, if skipping structures were to be formed by other fluids, scientists began some computer simulation. The result: "This effect also occurs with water," explained Tobias Vogt. "But because more water is more liquid than liquid, and the heat is less, the phenomenon is much weaker."

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