Ubiquity of particle–vortex interactions in turbulent counterflow of superfluid helium

Švančara, P.; Duda, Daniel; Hrubcová, Petra; Rotter, M.; Skrbek, L.; Mantia, M. La; Durozoy, Emeric; Diribarne, Pantxo; Rousset, Bernard; Bourgoin, Mickaël; Gibert, Mathieu

doi:10.1017/jfm.2020.1017

Cited by 9 publications

(7 citation statements)

References 37 publications

(121 reference statements)

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“…Švančara et al. (2021), for the estimate of we employed the Stokes formula, assuming spherical particles with radius equal to m (the density of solid deuterium is set to , and the fluid temperature is set to K).…”

Section: Resultsmentioning

confidence: 99%

“…We employ specifically the particle tracking velocimetry technique, which is based on following the flow-induced motions of relatively small particles – see Švančara et al. (2021) for another recent example. Our -sized particles are made of solid deuterium; they are illuminated with a mm thick laser sheet crossing the symmetry axis of the set-up, and their motion is captured by a high-speed digital camera with a narrow depth of field.…”

Section: Methodsmentioning

confidence: 99%

“…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%

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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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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Coherent propagation of vortex rings at extremely high Reynolds numbers

Švančara

Mantia

2022

J. Fluid Mech.

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“…Švančara et al. 2021). More generally, our work neatly demonstrates that quantitative comparisons between particle trajectories obtained under different experimental conditions can be performed using pseudovorticity maps, taking also into account particle concentration and inertia.…”

Section: Discussionmentioning

confidence: 98%

“…The cryogenic flows of this unique liquid are routinely visualized and several PTV studies have been reported to date – see Švančara et al. (2021) for a recent example. However, at a given time, one can usually identify the positions of about 100 particles within a 1 Mpixel image, each particle having an apparent size of a few pixels.…”

Section: Introductionmentioning

confidence: 99%