In a joint research with Keio University, a research group led by Satoshi Yui, a graduate student of Osaka City University, and Professor Makoto Tsubota, the velocity distribution of normal fluid is greatly deformed with the development of quantum turbulence generated in an extremely low temperature state. I found that.It is said to be a result that greatly approaches the elucidation of turbulence, which has been a mystery for hundreds of years.
In nature, there are many "turbulent flows" in which the flow of gas and liquid is complicatedly disturbed.About 500 years ago, Leonardo da Vinci drew a sketch of turbulence and speculated that "turbulence consists of vortices."However, the mechanism and characteristics of turbulent flow have not been fully elucidated so far.
It has been reported that "superconductivity" in which the electric resistance of a metal becomes zero when a substance becomes extremely low temperature, and "superfluidity" in which the viscosity of a liquid becomes zero in a fluid.The superfluid phenomenon observed in liquid helium is known to be dominated by quantum mechanics.
Landau, a theoretical physicist, proposed a "two-fluid model" in which a superfluid that has lost its viscosity and a normal fluid that has viscosity are mixed for this superfluid phenomenon.The two-fluid model has greatly contributed to the elucidation of various phenomena in cryogenic physics.On the other hand, superfluids expressed by the deformation and transport of quantum vortices and normal fluids that fill the space without gaps, such as water, are heterogeneous and complicated, so calculations to explain the experimental results are still impossible.
The research group carries out large-scale numerical calculations by combining an equation that expresses the quantum vortex responsible for the motion of superfluid with a mathematical formula and an equation that expresses the flow of normal fluid (Navier-Stokes equation).As a result, it was shown for the first time in the world that the velocity distribution of normal fluid undergoes a large deformation when a quantum vortex grows and creates a fluffy quantum turbulence.This validated Da Vinci's ideas.
It is expected that this achievement will lead to the demonstration of more complicated fluids and turbulent behavior, and eventually to the elucidation of turbulent phenomena.
