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Fully Coupled Two-Fluid Dynamics in Superfluid ^{4}He: Anomalous Anisotropic Velocity Fluctuations in Counterflow
Satoshi Yui1, Hiromichi Kobayashi1,2, Makoto Tsubota3
1Research and Education Center for Natural Sciences, Keio University, 4-1-1 Hiyoshi, Kohoku-ku, Yokohama 223-8521, Japan.
Physical Review Letters
|May 2, 2020
Summary
We simulated superfluid helium-4 thermal counterflow, revealing anisotropic velocity fluctuations in the normal fluid due to quantum turbulence. These findings align with experiments, validating our two-fluid dynamics model.
Area of Science:
- Quantum fluid dynamics
- Superfluidity physics
- Statistical mechanics
Background:
- Superfluid helium-4 exhibits complex two-fluid behavior.
- Thermal counterflow involves interactions between quantized vortices and the normal fluid.
- Understanding these interactions is key to superfluid dynamics.
Purpose of the Study:
- To numerically simulate the three-dimensional coupled dynamics of superfluid helium-4 in thermal counterflow.
- To analyze velocity fluctuations in the normal fluid caused by mutual friction with superfluid quantum turbulence.
- To investigate the anisotropic nature of these fluctuations.
Main Methods:
- Three-dimensional numerical simulations of coupled two-fluid dynamics.
- Analysis of velocity fluctuations in the normal fluid component.
- Comparison of streamwise and transverse fluctuation characteristics.
- Validation against experimental data and simple models.
Main Results:
- Streamwise velocity fluctuations in the normal fluid show higher intensity and longer autocorrelation than transverse fluctuations.
- Anisotropic fluctuation behavior is observed.
- Numerical results are consistent with prior visualization experiments.
Conclusions:
- The fully coupled two-fluid dynamics model is validated by the agreement with experimental observations.
- The study provides insights into the anisotropic nature of fluctuations in superfluid helium-4 counterflow.
- This work supports further investigation of outstanding problems in superfluid two-fluid systems.
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