Effect of the Phase Boundary Kinetics of a Helium Crystal on Motion in a Superfluid Liquid

Tsymbalenko, V. L.

doi:10.1007/s10909-022-02685-0

Cited by 2 publications

(1 citation statement)

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“…The accuracy of our theory will be improved through future measurements of the drag force or the effective dynamic viscosity η ′ n on an object with various shapes in a wide range of temperatures. Furthermore, more experimental data under higher pressures is required to facilitate precise extension of the theory to the systems of 4 He crystal [12,[46][47][48][49]. As in the experiments, we can track the detailed motion of falling objects in He-II and extract more useful information regarding the terminal speed and the property of the chaotic motion owing to the turbulent wake of the superfluid component.…”

Section: Summary and Prospectsmentioning

confidence: 99%

Quantum viscosity and the Reynolds similitude in quantum liquid He-II

Takeuchi¹

2023

Preprint

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Reynolds similitude, a key concept in hydrodynamics, states that two phenomena of different length scales with a similar geometry are physically identical. Flow properties are universally determined in a unified way in terms of the Reynolds number R (dimensionless, ratio of inertial to viscous forces in incompressible fluids). For example, the drag coefficient cD of objects with similar shapes moving in fluids is expressed by a universal function of R. Certain studies introduced similar dimensionless numbers, that is, the superfluid Reynolds number Rs, to characterize turbulent flows in superfluids. However, the applicablity of the similitude to inviscid quantum fluids is nontrivial as the original theory is applicable to viscous fluids. This study proposed a method to verify the similitude using current experimental techniques in quantum liquid He-II. A highly precise relation between cD and Rs was obtained in terms of the terminal speed of a macroscopic body falling in He-II at finite temperatures across the Knudsen (ballistic) and hydrodynamic regimes of thermal excitations. Reynolds similitude in superfluids can facilitate unified mutual development of classical and quantum hydrodynamics.

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