The Dynamics of Vortex Generation in Superfluid 3He-B

Graaf, R. de; Hänninen, Risto; Chagovets, T. V.; Eltsov, V. B.; Krusius, M.; Solntsev, R. E.

doi:10.1007/s10909-008-9827-1

Cited by 8 publications

(9 citation statements)

References 49 publications

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“…The turbulent process consists of two stages. First during the precursor, the number of vortices N increases linearly with time at a rate _ N ∼ 1 s −1 (15,25). Later in the turbulent burst, N suddenly increases close to the equilibrium number N eq .…”

Section: Coarse-grained Superfluid Dynamics and Mutual Frictionmentioning

confidence: 96%

“…In his pioneering work, Reynolds (31) demonstrated the influence of the entrance to the pipe and the quality of his long straight flow channel on the downstream vorticity and turbulence. For superfluid pipe flow, technical problems of this kind have not yet been solved in experiments, but the transition can be studied using numerical calculations (25).…”

Section: Coarse-grained Superfluid Dynamics and Mutual Frictionmentioning

confidence: 99%

See 1 more Smart Citation

Quantum turbulence in superfluids with wall-clamped normal component

Eltsov

Hänninen

Krusius

2014

Proc. Natl. Acad. Sci. U.S.A.

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In Fermi superfluids, such as superfluid 3 He, the viscous normal component can be considered to be stationary with respect to the container. The normal component interacts with the superfluid component via mutual friction, which damps the motion of quantized vortex lines and eventually couples the superfluid component to the container. With decreasing temperature and mutual friction, the internal dynamics of the superfluid component becomes more important compared with the damping and coupling effects from the normal component. As a result profound changes in superfluid dynamics are observed: the temperature-dependent transition from laminar to turbulent vortex motion and the decoupling from the reference frame of the container at even lower temperatures.superfluid Reynolds number | vortex tension | vortex front | rotating flow | pipe flow I n this paper, we consider the motion of quantized vortices in superfluids, where the normal component is clamped to the walls of the container; that is, it is stationary in a reference frame moving with the wall. This situation can be experimentally realized in superfluid 3 He. In such systems, turbulent motion can occur only in the superfluid component and thus, in principle, is easier to analyze. Here the role of the normal fluid is twofold: first, it provides friction in the superfluid motion, which is mediated by quantized vortices and works over a wide range of length scales. Second, it provides a coupling to the container walls, which acts uniformly over the whole volume of the superfluid. This situation is quite unlike classical turbulence, where viscous dissipation operates only at the small Kolmogorov scale and coupling to the walls is provided by thin boundary layers.As a result, a variety of new phenomena is observed in experiments and numerical simulations as a function of temperature. These phenomena are controlled by the normal-fluid density. At the highest temperatures, turbulent motion is suppressed completely. When the temperature decreases, a sharp transition to turbulence is seen. The transition can be characterized by a superfluid Reynolds number, which is composed of the internal friction parameters of the superfluid and is independent of velocity. When turbulence is triggered by a localized perturbation of the laminar flow, the critical value of the Reynolds number is found to scale with the strength of the perturbation.When the temperature decreases further, friction from the normal component rapidly vanishes. The overall dissipation rate in quantum turbulence remains nevertheless finite, owing to the contribution from the turbulent energy cascade, and reaches a temperatureindependent value in the zero-temperature limit. This zero-temperature dissipation can be characterized by an effective viscosity or friction. It is found, however, that coupling to the walls is not essentially improved by the turbulence and can potentially become very small. At the lowest temperatures the concept of a single effective friction breaks down; for the proper descriptio...

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Section: Coarse-grained Superfluid Dynamics and Mutual Frictionmentioning

confidence: 96%

Section: Coarse-grained Superfluid Dynamics and Mutual Frictionmentioning

confidence: 99%

Quantum turbulence in superfluids with wall-clamped normal component

Eltsov

Hänninen

Krusius

2014

Proc. Natl. Acad. Sci. U.S.A.

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“…It is possible that a smaller value of the velocity difference between the two components (vn − vs), near the boundaries, may explain this result. Turbulence is caused by the vortex instability at the boundaries [41], and the level of turbulence that can be supported depends on the counterflow velocity at the boundaries. These results are illustrated in Fig.…”

Section: Counterflow Turbulencementioning

confidence: 99%

“…However, before this steady state is reached, turbulence may appear, especially at low temperatures when the mutual friction is low [49,50,51]. The onset and initialization of turbulence has been attributed to the instability that originates from interaction of the vortex with the container walls [52,41,51].…”

Section: Coherent Structures Under Rotationmentioning

confidence: 99%

Vortex filament method as a tool for computational visualization of quantum turbulence

Hänninen

Baggaley

2014

Proc. Natl. Acad. Sci. U.S.A.

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The vortex filament model has become a standard and powerful tool to visualize the motion of quantized vortices in helium superfluids. In this article, we present an overview of the method and highlight its impact in aiding our understanding of quantum turbulence, particularly superfluid helium. We present an analysis of the structure and arrangement of quantized vortices. Our results are in agreement with previous studies showing that under certain conditions, vortices form coherent bundles, which allows for classical vortex stretching, giving quantum turbulence a classical nature. We also offer an explanation for the differences between the observed properties of counterflow and pure superflow turbulence in a pipe. Finally, we suggest a mechanism for the generation of coherent structures in the presence of normal fluid shear.T urbulence in fluid flows is universal, from galactic scales generated by supernova explosions down to an aggressively stirred cup of coffee. There is no debate that turbulence is important, yet no satisfactory theory exists. Turbulence is built by rotational motions, typically over a wide range of scales, interacting and mediating a transfer of energy to scales at which it can be dissipated effectively. The motivation for Küchemann's famous quote "vortices are the sinews and muscles of fluid motions" is clear. If this is true, then quantum turbulence (QT) represents the skeleton of turbulence and offers a method of attacking the turbulence problem in perhaps its simplest form.QT is a tangle of discrete, thin vortex filaments, each carrying a fixed circulation. It typically is studied in cryogenically cooled helium (1, 2) and, more recently, in atomic Bose-Einstein condensates (3). These substances are examples of so-called quantum fluids: fluids for which certain physical properties cannot be described classically but depend on quantum mechanics. The quantization of vorticity is one marked difference between quantum and classical fluids. Another is their two-fluid nature; they consist of a viscous normal fluid component and an inviscid superfluid component coupled by a mutual friction. The relative densities of these components are temperature dependent.Despite these marked differences, it is now the consensus opinion that QT is capable of exhibiting many of the statistical properties of classical turbulence, including the famed Kolmogorov scaling (4). Hence, QT has the potential to offer new insights into vortex dynamics and the role they play in the dynamics of turbulence. In addition, QT offers many interesting problems in its own right. However, QT, more so than classical turbulence, suffers from poor visualization of the flow in experiments because of the extremely low temperatures involved. Hence, numerical methods are necessary to aid our understanding of the structure of quantized vortices in different forms of turbulence, acting as a guide for both experiments and theory. In this article, we discuss a widely used numerical model of QT, the vortex filament model (VFM). VFMIn the ...

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“…As explained in the next section, when vortex lines are not all perfectly aligned with the rotation axis, the effective value of λ (determined by the average effect of all vortex lines) may change. At low temperatures vortex formation proceeds typically through instabilities and interactions of the existing vortices, often in a localized turbulent burst [10]. The vortex configuration created in such a process is far from the equilibrium one and its relaxation to the equilibrium state is impeded by the existence of many local energy minima in the vortex configurations.…”

Section: Determination Of the Core Contributionmentioning

confidence: 99%

Vortex Core Contribution to Textural Energy in 3He–B Below 0.4T c

et al. 2010

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Vortex lines affect the spatial order-parameter distribution in superfluid 3 He-B owing to superflow circulating around vortex cores and due to the interaction of the order parameter in the core and in the bulk as a result of superfluid coherence over the whole volume. The step-like change of the latter contribution at 0.6T c (at a pressure of 29 bar) signifies the transition from axisymmetric cores at higher temperatures to broken-symmetry cores at lower temperatures. We extended earlier measurements of the core contribution to temperatures below 0.2T c , in particular searching for a possible new core transition to lower symmetries. As a measuring tool we track the energy levels of magnon condensate states in a trap formed by the order-parameter texture.

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The Dynamics of Vortex Generation in Superfluid 3He-B

Cited by 8 publications

References 49 publications

Quantum turbulence in superfluids with wall-clamped normal component

Quantum turbulence in superfluids with wall-clamped normal component

Vortex filament method as a tool for computational visualization of quantum turbulence

Vortex Core Contribution to Textural Energy in 3He–B Below 0.4T c

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