On the determination of vortex ring vorticity using Lagrangian particles

Outrata, Ondřej; Pavelka, Michal; Hron, J.; Mantia, M. La; Polanco, Juan Ignacio; Krstulovic, Giorgio

doi:10.1017/jfm.2021.662

Cited by 8 publications

(8 citation statements)

References 36 publications

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“…One can see clearly that particle trajectories are significantly bent near the ring core, and that the ring moves upwards along a straight line. Note, however, that, in order to get an even clearer picture, one would need more particles, especially to track the ring in time, as was demonstrated, for example, by Outrata et al (2021) in their figure 1, where the displayed ring is larger and slower than the present ones, with Re ≈ 10 5 -see again Švančara et al (2020). Indeed, as detailed below, flow visualization data are employed here to show that the studied flows are restricted in space and time, but unfortunately, their detailed structure, e.g.…”

Section: Methodsmentioning

confidence: 67%

“…Note, however, that, in order to get an even clearer picture, one would need more particles, especially to track the ring in time, as was demonstrated, for example, by Outrata et al. (2021) in their figure 1, where the displayed ring is larger and slower than the present ones, with – see again Švančara et al. (2020).…”

Section: Methodsmentioning

confidence: 70%

“…The used visualization technique is based on tracking the flow-induced motions of relatively small solid particles dispersed in the fluid. The particle positions and velocities are then employed to calculate the Lagrangian pseudovorticity, which is a scalar quantity linked directly to the underlying flow vorticity (Outrata et al 2021). In short, Švančara et al (2020) showed that in the range of investigated parameters, the observed ring motions are consistent with a similarity theory developed for turbulent vortex rings propagating in Newtonian fluids (Maxworthy 1974;Glezer & Coles 1990;Gan & Nickels 2010).…”

Section: Introductionmentioning

confidence: 62%

“…The particle positions and velocities are then employed to calculate the Lagrangian pseudovorticity, which is a scalar quantity linked directly to the underlying flow vorticity (Outrata et al. 2021). In short, Švančara et al.…”

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: Methodsmentioning

confidence: 67%

Section: Methodsmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 62%

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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“…This allows us to compute the Lagrangian pseudovorticity θ on a chosen grid, as in previous works, see e.g. [6]. Specifically, we set…”

Section: Methodsmentioning

confidence: 99%

Visualization of the Starting Vortex Shed by a Cylinder Accelerating in Superfluid Helium-4: Preliminary Results

Blaha,

La Mantia

2024

Topical Problems of Fluid Mechanics 2024

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A cylinder of elliptical cross-section is accelerated from rest in superfluid helium-4, a unique cryogenic liquid, characterized by very small values of kinematic viscosity. The starting vortex generated by the cylinder is visualized using the particle tracking velocimetry technique, at different values of fluid temperature and cylinder acceleration. The vortex trajectory and strength are estimated from the particles’ positions and velocities, in view of comparing the behaviour of the shed vortices in various experimental conditions. We specifically find that the vortex trajectory does not appear to depend appreciably on the fluid temperature and cylinder acceleration magnitude, while the latter seems to influence significantly the vortex strength. Overall, the preliminary results presented here show that further studies are required to assess in a quantitative way similarities and differences with analogous flows of Newtonian fluids.

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