Study on the Curvature of Lagrangian Trajectories in Thermal Counterflow

Sakaki, N.; Maruyama, Takumi; Tsuji, Yoshiyuki

doi:10.1007/s10909-022-02734-8

Cited by 2 publications

(2 citation statements)

References 16 publications

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“…Up to now, three families of particles have been used as Lagrangian probes: (i) solid particles at room temperature with a density that matches the fluid density (hollow glass sphere) (19) or nonbuoyant nanoparticles (20), (ii) hydrogen (21,22) or deuterium (23)(24)(25) flakes, and (iii) metastable He 2 * molecule (26). It is hard to conclude firmly on what the first two kinds of particles are tracking exactly (27)(28)(29), while the third kind traces the normal fluid component only above 1 K and could be trapped on vortices bellow 0.5 K (30). Coming back to solid particles, the seminal work done in the early aughts (21) convinced the community that these particles could, under certain conditions, decorate quantum vortices (31)(32)(33)(34).…”

Section: Introductionmentioning

confidence: 99%

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He

et al. 2023

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Quantum vortices are a core element of superfluid dynamics and elusively hold the keys to our understanding of energy dissipation in these systems. We show that we are able to visualize these vortices in the canonical and higher-symmetry case of a stationary rotating superfluid bucket. Using direct visualization, we quantitatively verify Feynman’s rule linking the resulting quantum vortex density to the imposed rotational speed. We make the most of this stable configuration by applying an alternative heat flux aligned with the axis of rotation. Moderate amplitudes led to the observation of collective wave mode propagating along the vortices, and high amplitudes led to quantum vortex interactions. When increasing the heat flux, this ensemble of regimes defines a path toward quantum turbulence in rotating 4 He and sets a baseline to consolidate the descriptions of all quantum fluids.

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Section: Introductionmentioning

confidence: 99%

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He

et al. 2023

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“…The latter is specifically the case of thermal counterflow, which is a very peculiar flow of superfluid He, generated by a heat source and characterized by the fact that, on average, at large enough scales, the fluid components flow in opposite directions, with the superfluid component flowing towards the heater, in order to conserve the null mass flow rate, and the normal fluid component carrying entropy away from the heat source; see Švančara et al. (2021) and Sakaki, Maruyama & Tsuji (2022) for recent experimental investigations of thermal counterflow.…”

Section: Introductionmentioning

confidence: 99%

Coherent propagation of vortex rings at extremely high Reynolds numbers

Švančara

Mantia

2022

J. Fluid Mech.

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We take advantage of the extremely small kinematic viscosity of superfluid $^4$ He to investigate the propagation of macroscopic vortex rings at Reynolds numbers between $2 \times 10^4$ and $4 \times 10^6$ . These inhomogeneous flow structures are thermally generated by releasing short power pulses into a small volume of liquid, open to the surrounding bath through a vertical tube $2$ mm in diameter. We study specifically the ring behaviour between $1.30$ and $1.80$ K using the flow visualization and second sound attenuation techniques. From the obtained data sets, containing more than $2600$ realizations, we find that the rings remain well-defined in space and time for distances up to at least $40$ tube diameters, and that their circulation depends significantly on the travelled distance, in a way similar to that observed for turbulent vortex rings propagating in Newtonian fluids. Additionally, the ring velocity and circulation appear to be influenced solely by a single, experimentally accessible parameter, combining the liquid temperature with the magnitude and duration of the power pulse. Overall, our results support the view that macroscopic vortex rings moving in superfluid $^4$ He closely resemble their Newtonian analogues, at least in the absence of significant thermal effects and at sufficiently large flow scales.

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Study on the Curvature of Lagrangian Trajectories in Thermal Counterflow

Cited by 2 publications

References 16 publications

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He

Coherent propagation of vortex rings at extremely high Reynolds numbers

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Study on the Curvature of Lagrangian Trajectories in Thermal Counterflow

Cited by 2 publications

References 16 publications

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating 4 He

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating 4 He

Coherent propagation of vortex rings at extremely high Reynolds numbers

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Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He

Direct visualization of the quantum vortex lattice structure, oscillations, and destabilization in rotating ⁴ He