Forces in the flow of liquid helium II

Heijden, G. H. M. van der; Voogt, W.J.P. de; Kramers, H.C.

doi:10.1016/0031-8914(72)90201-7

Cited by 26 publications

(1 citation statement)

References 19 publications

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“…5 Suppression of the CO in the stainless steel system was achieved by The spin polarization of field-emitted electrons from the (100) plane of field-evaporated Ni single-crystal tips is observed to decrease from -(3.0 ±1)% to (0 ± 1)% upon hydrogen adsorption (full coverage). We interpret these results as evidence for a strong reduction of the ferromagnetism of the d electrons of the Ni surface atoms upon hydrogen chemisorption.…”

Section: Heat Flux (Mwcm-2 )mentioning

confidence: 99%

Vortex-Line Density Fluctuations in Turbulent Superfluid Helium

Mantese¹,

Bischoff²,

Moss

1977

Phys. Rev. Lett.

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We present measurements of the equilibrium and mean-square fluctuation in vortexline density in turbulent He II. The equilibrium values are in good agreement with the Vinen theory and other current experimental results. The fluctuating quantities are described by the general instability theory reviewed by Haken.The phenomenological theory due to Vinen 1 has proven to be a remarkably accurate description of the equilibrium state of turbulent He II. The theory is based on a rate equation L = L g -L a , where L is the time rate of change of vortex-line density, and L g and L a are the growth and annihilation rates, respectively. The theory predicts thatwhere Xi, X2> ^> anc * & are dimensionless quantities of order unity, K = 0.997 xlO" 3 cm 2 sec" 1 is the circulation quantum, d is a characteristic length associated with the channel cross section, v = v s -v n is the counterflow velocity, where v s and v n are the superfluid and normal-fluid velocities, averaged both in time and over the channel cross section, L is the vortex-line density in the channel, and p n and p are the normal-and total fluid densities. The equilibrium solution, L = 0, is given bywhere 0= (-nXiBp n v/x 2 Kp). By measuring pressure and temperature gradients in small-diameter glass tubes, Childers and Tough 2 have provided recent values for the dimensionless quantities and the first detailed study of the instability in Lg, which marks the onset of line-density growth at )3 cl =4a/d, in a regime where the normal-fluid flow is laminar. In addition, they have discovered a second instability, at /3 c2 »0 cl , which describes the transition to turbulent normal-fluid flow. 3 Previously, the existence of the two regimes had been observed by Brewer and Edwards 4 and van der Heijden, de Boogt, and Kramers 5 using a similar experimental technique. The dependence of L a on L 0 2 , shown in Eq. (1), was demonstrated, 6 * 7 and measurements of the dimensionless quantities 7 were provided. The agreement among the works cited is quite good even though one experiment 8 has demonstrated the error of the assumption in the Vinen theory that the average velocity of the vortex tangle satisfies v L^vs . Finally, Schwarz 9 has provided a new equilibrium turbulence theory which is in good quantitative agreement with Eq. (2), and accurately predicts the results of Ref. 8.In this Letter, we present the first quantitative measurements of the time-dependent line-density fluctuations 10 6L(t), at T~ 1.64 K, and we use a generalized potential 11 to predict 6L in terms of a parameter 6j3/j3 0 representing the relative intensity of fluctuations in the counterflow velocity.Measurements of L 0 and 6L(t) were obtained from the attenuation of second sound in one of the five cavities shown perpendicular to the channel in Fig.

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Section: Heat Flux (Mwcm-2 )mentioning

confidence: 99%