Particle Image Velocimetry Studies of Counterflow Heat Transport in Superfluid Helium II

Sciver, S.W. Van; Fuzier, Sylvie; Xu, Ting

doi:10.1007/s10909-007-9375-0

Cited by 18 publications

(20 citation statements)

References 14 publications

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“…At low and moderate pressures m p ∼ 3m 3 . The semiclassical Hamiltonian equations of quasiparticle motion can be written as (37) dr dt = e p ffiffiffiffiffiffiffiffiffiffiffiffiffiffi ffi e 2 p + Δ 2 q p m * + v; dp dt = − ∂ ∂r ðp · vÞ; [12] where e p = p 2 =ð2m * Þ − e F is the "kinetic" energy of a quasiparticle relative to the Fermi energy, e F . The flow field vðr; tÞ, which defines the motion of vortices at low temperatures, is obtained by the Biot-Savart integral over all vortex lines.…”

Section: Numerical Simulations Of Andreev Scatteringmentioning

confidence: 99%

“…There has been a great deal of renewed interest in quantum turbulence in recent years owing to several factors: quantum turbulence was discovered in superfluid 3 He (6)(7)(8), techniques were developed to extend the study of quantum turbulence in superfluid 4 He to very low temperatures (9,10), imaging techniques were developed to visualize superfluid turbulence at higher temperatures (11)(12)(13)) (see the review in ref. 14), mechanical resonator techniques were developed for quantum turbulence (15)(16)(17)(18), and quantum turbulence was studied in dilute gases (19,20); there were many important theoretical developments, for example refs.…”

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confidence: 99%

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Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B

Fisher

Jackson

Sergeev

et al. 2014

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

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Andreev reflection of quasiparticle excitations provides a sensitive and passive probe of flow in superfluid 3 He-B. It is particularly useful for studying complex flows generated by vortex rings and vortex tangles (quantum turbulence). We describe the reflection process and discuss the results of numerical simulations of Andreev reflection from vortex rings and from quantum turbulence. We present measurements of vortices generated by a vibrating grid resonator at very low temperatures. The Andreev reflection is measured using an array of vibrating wire sensors. At low grid velocities, ballistic vortex rings are produced. At higher grid velocities, the rings collide and reconnect to produce quantum turbulence. We discuss spatial correlations of the fluctuating vortex signals measured by the different sensor wires. These reveal detailed information about the formation of quantum turbulence and about the underlying vortex dynamics. Quantum turbulence in superfluid 4 He has been studied for many decades (3-5). There has been a great deal of renewed interest in quantum turbulence in recent years owing to several factors: quantum turbulence was discovered in superfluid 3 He (6-8), techniques were developed to extend the study of quantum turbulence in superfluid 4 He to very low temperatures (9, 10), imaging techniques were developed to visualize superfluid turbulence at higher temperatures (11-13) (see the review in ref. 14), mechanical resonator techniques were developed for quantum turbulence (15-18), and quantum turbulence was studied in dilute gases (19,20); there were many important theoretical developments, for example refs. 21-26, and numerical methods were enormously improved (27-29) to complement and better interpret experimental results.In this article, we discuss quantum turbulence generated by vibrating grids in superfluid 3 He-B at low temperatures, where the normal fluid component is very small. The primary thermal excitations in 3 He are quasiparticle and quasihole excitations (30). At low temperatures, the excitation mean free path between collisions vastly exceeds the experimental dimensions. In this ballistic regime, excitations move independently and normally scatter only with the container walls. The normal fluid concept no longer applies because there is no collective motion of excitations.In addition to normal scattering, excitations can also undergo Andreev reflection. Andreev scattering produces nearly perfect retroreflection of excitations with very little momentum transfer: Quasiparticles become quasiholes, and vice versa. This provides an ideal probe for vortices and quantum turbulence at low temperatures. Andreev Scattering from Superfluid FlowThe dispersion curve for excitations is shown in Fig. 1A. The excitation group velocity v g = dE=dp is parallel to the momentum for quasiparticles that have p > p F , where p F is the Fermi momentum and is antiparallel to the momentum for quasiholes that have p < p F . The dispersion curve is tied to the reference frame of the superfluid. So, accordi...

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Section: Numerical Simulations Of Andreev Scatteringmentioning

confidence: 99%

mentioning

confidence: 99%

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B

Fisher

Jackson

Sergeev

et al. 2014

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

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“…10) The superfluid motion around a locally straight vortex can be expressed in cylindrical coordinates fs; ; zg as v ¼ =2s, where ¼ h=m ¼ 9:97 Â 10 À4 cm 2 /s is the quantum of circulation, h Planck's constant, and m the mass of a 4 He atom. Trapping a particle or bubble on the vortex core causes a reduction in the kinetic energy owing to the displaced circulating superfluid helium.…”

Section: Particle Trapping Mechanismmentioning

confidence: 99%

“…Polymer micro-spheres and hydrogen isotopes have been used for particle image velocimetry (PIV) measurements [1][2][3][4][5] and solid hydrogen tracers have been used to visualize the structure and dynamics of quantized vortices. [6][7][8][9] However, the dynamics of tracers in superfluid flows are more complicated than in viscous fluids since the particles can interact with the quantized vortices 10) in addition to the normal fluid.…”

Section: Introductionmentioning

confidence: 99%

Visualization of Superfluid Helium Flow

et al. 2008

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We discuss an experimental technique to visualize motion in the bulk of superfluid 4 He by tracking micron-sized solid hydrogen tracers. The behavior of the tracers is complex since they may be trapped by the quantized vortices while also interacting with the normal fluid via Stokes drag. We discuss the mechanism by which tracers may be trapped by quantized vortices as well as the dependencies on hydrogen volume fraction, temperature, and flow properties. We apply this technique to study the dynamics of a thermal counterflow. Our observations serve as a direct confirmation of the two-fluid model as well as a quantitative test of the normal fluid velocity dependence on the applied heat flux.

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“…Simultaneous turbulence in both fluids in a counterflow must be different, and it would be a type of turbulence that is new to physics. Past experiments on the visualization of thermal counterflow have used micron-sized tracer particles formed from polymer spheres or solid hydrogen, and they have been based on either particle image velocimetry [8] or particle tracking techniques [9]. The particle image velocimetry data obtained at large heat fluxes are hard to interpret since micron-sized particles can be trapped on the quantized vortex lines.…”

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confidence: 99%

Laminar, turbulent, or doubly turbulent?

Barenghi¹

2010

Physics

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Heat is transferred in superfluid 4 He via a process known as thermal counterflow. It has been known for many years that above a critical heat current the superfluid component in this counterflow becomes turbulent. It has been suspected that the normal-fluid component may become turbulent as well, but experimental verification is difficult without a technique for visualizing the flow. Here we report a series of visualization studies on the normal-fluid component in a thermal counterflow performed by imaging the motion of seeded metastable helium molecules using a laser-induced-fluorescence technique. We present evidence that the flow of the normal fluid is indeed turbulent at relatively large velocities. Thermal counterflow in which both components are turbulent presents us with a theoretically challenging type of turbulent behavior that is new to physics. DOI: 10.1103/PhysRevLett.105.045301 PACS numbers: 67.25.dk, 29.40.Gx, 47.27.Ài The superfluid phase of liquid 4 He exhibits two-fluid behavior [1]: a normal fluid, carrying all the thermal energy, coexists with a superfluid component. The proportion of superfluid falls from unity to zero as the temperature T rises from zero to the transition [1]. In a thermal counterflow, the normal-fluid velocity v n is related to the heat flux q by q ¼ STv n ;( 1) where is the total density and S is the entropy per unit mass [1]. Above a certain critical heat flux, superflow is known to become turbulent. This quantum turbulence takes the form of a disorganized tangle of quantized vortex lines [2,3]. A mutual friction force between the two fluids arises through the interaction between the quantized vortices and the normal fluid [4]. This type of quantum turbulence is maintained by the relative motion of the two fluids, through processes that are reasonably well understood [2,3]. Features in the observed relation between vortex density and heat flux suggest that the normal fluid may also become turbulent, and mutual friction has been shown theoretically to induce an instability in the laminar flow of the normal fluid [5]. Satisfactory evidence for such normalfluid turbulence can come only from a visualization of the normal-fluid flow. Techniques for such visualization have recently started to be developed. Turbulence in both fluids has been observed in other types of flow in liquid helium [6], such as that behind a moving grid [7]. But in those cases the two fluids are not forced to have any relative motion and behave like a single classical fluid, exhibiting a Kolmogorov energy spectrum [1]. Simultaneous turbulence in both fluids in a counterflow must be different, and it would be a type of turbulence that is new to physics. Past experiments on the visualization of thermal counterflow have used micron-sized tracer particles formed from polymer spheres or solid hydrogen, and they have been based on either particle image velocimetry [8] or particle tracking techniques [9]. The particle image velocimetry data obtained at large heat fluxes are hard to interpret since micron-s...

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Particle Image Velocimetry Studies of Counterflow Heat Transport in Superfluid Helium II

Cited by 18 publications

References 14 publications

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B

Visualization of Superfluid Helium Flow

Laminar, turbulent, or doubly turbulent?

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Particle Image Velocimetry Studies of Counterflow Heat Transport in Superfluid Helium II

Cited by 18 publications

References 14 publications

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in 3 He-B

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in 3 He-B

Visualization of Superfluid Helium Flow

Laminar, turbulent, or doubly turbulent?

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Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B

Andreev reflection, a tool to investigate vortex dynamics and quantum turbulence in ³ He-B