Falling<sup>4</sup>He crystals in superfluid

Nomura, R.; Yoshida, Taichi; Tachiki, Akira; Okuda, Y.

doi:10.1088/1367-2630/16/11/113022

Cited by 10 publications

(4 citation statements)

References 24 publications

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“…In the metastable superfluid at a few millibar above the melting pressure, an acoustic wave pulse was applied by the upper transducer to initiate nucleation of a hexagonal-closed-packed (hcp) 4 He seed crystal on the transducer surface [13,21,30]. The crystal eventually fell in the superfluid and landed on the bottom.…”

Section: Methodsmentioning

confidence: 99%

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Nomura

Abe²,

Okuda

2017

New J. Phys.

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The relaxation dynamics of the crystal-superfluid interface of 4 He after deformation induced by acoustic radiation pressure was investigated for various crystal orientations. The melting relaxation after growth was approximately 10 times slower than the growth relaxation after melting for vicinal surfaces and facets, while both relaxation times were consistent with each other for rough surfaces. The asymmetry in the time constant between the melting and growth of vicinal surfaces and facets can be qualitatively explained as the effect of superflow induced by local rapid interface motion, such as a quick rounding of facet edges of the 4 He crystal. Rough surfaces move more isotropically and no significant local rapid interface motion is induced; therefore, their relaxation is likely to be symmetric with a minimal effect of superflow. While the growth relaxation was simply back to the initial shape in a single stage, the melting relaxation was much more complex with multiple stages and the exhibition of various anomalous shapes depending on temperature. Anomalous shapes such as needle-like shapes during melting have a larger curvature and higher energy and thus should have disappeared more quickly than the growth shape with a smaller curvature, but they were considerably stable and disappeared slowly. This counter-intuitive asymmetry suggests the significant role of superflow in the relaxation process. 4 He quantum crystals in superfluid is the exceptional material to be manipulated by small driving forces such as heat, gravity, and flow [6-13], because they grow extremely fast at low temperatures and play a very important role in understanding the fundamental aspects of crystal growth physics [14][15][16][17]. In previous reports, we have demonstrated that acoustic radiation pressure, which is the small second-order acoustic force usually not relevant to the crystallization process [18,19], induces both growth and melting of 4 He crystals and is a very useful tool to manipulate the interface in a desired orientation, even to a large extent [17,[20][21][22].

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Section: Methodsmentioning

confidence: 99%

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Nomura

Abe²,

Okuda

2017

New J. Phys.

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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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“…The phase kinetics plays a significant role even at the magnitudes of the kinetic growth coefficient K ∼ 0.2s/m. The question whether this model is applicable to the interpretation of the experiments of the Japanese group [6] should be answered negatively. The lower part of the crystal, as is seen in the shooting, has the well-visible facets.…”

Section: Next Motion Of the Crystalmentioning

confidence: 99%

“…The direct observation of the crystal shape transformation during the fall of the crystal is made by the Japanese group at 0.3 K using a high-speed camera [6]. The acceleration at which the crystal falls corresponds to the motion of a solid body with the adjoined mass equal to the mass of a half of the liquid displaced by the crystal.…”

Section: Introductionmentioning

confidence: 99%

The Effect of the Interphase Kinetics on the Motion of a Quantum Crystal in Superfluid Liquid

Tsymbalenko

2019

J Low Temp Phys

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The fall of a quantum crystal in the state of "burst-like growth" in a superfluid liquid is considered. The experimental data of the pressure variation in the container during the fall of a crystal are discussed. The model of the motion of the crystal is suggested taking the interface dynamics into account. The results for the numerical simulation of the fall of a crystal are consistent with the experimental data. We find a significant effect of the liquid-crystal interface kinetics on the hydrodynamics of the liquid flow encircling a crystal.

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Falling⁴He crystals in superfluid

Cited by 10 publications

References 24 publications

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

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

The Effect of the Interphase Kinetics on the Motion of a Quantum Crystal in Superfluid Liquid

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Falling4He crystals in superfluid

Cited by 10 publications

References 24 publications

Asymmetry in melting and growth relaxation of4He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of4He crystals in superfluid after manipulation by acoustic radiation pressure

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

The Effect of the Interphase Kinetics on the Motion of a Quantum Crystal in Superfluid Liquid

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Product

Resources

About

Falling⁴He crystals in superfluid

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure

Asymmetry in melting and growth relaxation of⁴He crystals in superfluid after manipulation by acoustic radiation pressure