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Titolo:
Frequency-dependent viscosity of xenon near the critical point
Autore:
Berg, RF; Moldover, MR; Zimmerli, GA;
Indirizzi:
Natl Inst Stand & Technol, Phys & Chem Properties Div, Gaithersburg, MD 20899 USA Natl Inst Stand & Technol Gaithersburg MD USA 20899 ersburg, MD 20899 USA NYMA Inc, Brook Pk, OH 44142 USA NYMA Inc Brook Pk OH USA 44142NYMA Inc, Brook Pk, OH 44142 USA
Titolo Testata:
PHYSICAL REVIEW E
fascicolo: 4, volume: 60, anno: 1999,
parte:, A
pagine: 4079 - 4098
SICI:
1063-651X(199910)60:4<4079:FVOXNT>2.0.ZU;2-L
Fonte:
ISI
Lingua:
ENG
Soggetto:
CLASSICAL FLUID; CRITICAL EXPONENT; CARBON-DIOXIDE; LIQUID; TEMPERATURE; VISCOMETER; GRAVITY; MODEL;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
--discip_EC--
Citazioni:
47
Recensione:
Indirizzi per estratti:
Indirizzo: Berg, RF Natl Inst Stand & Technol, Phys & Chem Properties Div, Gaithersburg, MD 20899 USA Natl Inst Stand & Technol Gaithersburg MD USA 20899 MD 20899 USA
Citazione:
R.F. Berg et al., "Frequency-dependent viscosity of xenon near the critical point", PHYS REV E, 60(4), 1999, pp. 4079-4098

Abstract

We used a novel, overdamped oscillator aboard the Space-Shuttle to measurethe viscosity eta of xenon near its critical density rho(c) and temperature T-c. In microgravity, useful data were obtained within 0.1 mK of T-c, corresponding to a reduced temperature t =(T- T-c)/T-c= 3 X 10(-7). Because they avoid the detrimental effects of gravity at temperatures two decades closer to T-c than the best ground measurements, the data directly reveal the expected power-law behavior eta proportional to t(-nu z eta). Here nu is the correlation length exponent, and our result for the viscosity exponent isz(eta)= 0.0690+/- 0.0006. (All uncertainties are one standard uncertainty. ) Our value for z(eta) depends only weakly on the form of the viscosity crossover function, and it agrees with the value 0.067+/- 0.002 obtained from a recent two-loop perturbation expansion [H. Hao, R.A. Ferrell, and J.K. Bhattacharjee, (unpublished)]. The measurements spanned the frequency range 2Hz less than or equal to f less than or equal to 12 Hz and revealed viscoelasticity when t less than or equal to 10(-5), further from T-c than predicted. The viscoelasticity's frequency dependence scales as Af tau, where tauis the fluctuation-decay time. The fitted value of the viscoelastic time-scale parameter A is 2.0+/-0.3 times the result of a one-loop perturbation calculation. Near T-c, the xenon's calculated time constant for thermal diffusion exceeded days. Nevertheless, the viscosity results were independent of the xenon's temperature history, indicating that the density was kept near rho(c) by judicious choices of the temperature versus time program. Deliberately bad choices led to large density :inhomogeneities. At t>10(-5), thexenon approached equilibrium much faster than expected, suggesting that convection driven by microgravity and by electric fields slowly stirred the sample. [S1063-651X(99)04210-5].

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Documento generato il 04/04/20 alle ore 21:48:08