Classical capillary turbulence on the surface of quantum liquid He-II

Superfluid helium-4 is a unique liquid for experimental study of capillary wave turbulence due to its very low viscosity. We have studied the influence of amplitude and spectral characteristics of the excitation force on the behavior of the turbulent cascade of capillary waves in the cylindrical cel...

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Hauptverfasser: Abdurakhimov, L.V., Brazhnikov, M.Yu., Remizov, I.A., Levchenko, A.A.
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Veröffentlicht: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2011
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spelling irk-123456789-1185742017-05-31T03:03:51Z Classical capillary turbulence on the surface of quantum liquid He-II Abdurakhimov, L.V. Brazhnikov, M.Yu. Remizov, I.A. Levchenko, A.A. 8th International Conference on Cryocrystals and Quantum Crystals Superfluid helium-4 is a unique liquid for experimental study of capillary wave turbulence due to its very low viscosity. We have studied the influence of amplitude and spectral characteristics of the excitation force on the behavior of the turbulent cascade of capillary waves in the cylindrical cell of diameter 30 mm. We have found that the experimental results can be explained within the framework of the wave turbulence theory (WTT) when the amplitude of pumping is relatively high. However, a very interesting phenomenon was observed at moderate amplitudes of harmonic surface excitation. It was detected the deviation of the turbulent spectrum from the power law function predicted by WTT at high frequencies — local maximum — that can be interpreted as wave energy accumulation. Our estimations show that the special case of wave turbulence is realized in our measurements, namely, discrete turbulence which is characterized by the strong influence of discreteness of cell resonant frequencies on the mechanism of the nonlinear interaction. 2011 Article Classical capillary turbulence on the surface of quantum liquid He-II / L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, A.A. Levchenko // Физика низких температур. — 2011. — Т. 37, № 5. — С. 512–516. — Бібліогр.: 21 назв. — англ. 0132-6414 PACS: 68.03.Kn, 47.27.Gs http://dspace.nbuv.gov.ua/handle/123456789/118574 en Физика низких температур Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic 8th International Conference on Cryocrystals and Quantum Crystals
8th International Conference on Cryocrystals and Quantum Crystals
spellingShingle 8th International Conference on Cryocrystals and Quantum Crystals
8th International Conference on Cryocrystals and Quantum Crystals
Abdurakhimov, L.V.
Brazhnikov, M.Yu.
Remizov, I.A.
Levchenko, A.A.
Classical capillary turbulence on the surface of quantum liquid He-II
Физика низких температур
description Superfluid helium-4 is a unique liquid for experimental study of capillary wave turbulence due to its very low viscosity. We have studied the influence of amplitude and spectral characteristics of the excitation force on the behavior of the turbulent cascade of capillary waves in the cylindrical cell of diameter 30 mm. We have found that the experimental results can be explained within the framework of the wave turbulence theory (WTT) when the amplitude of pumping is relatively high. However, a very interesting phenomenon was observed at moderate amplitudes of harmonic surface excitation. It was detected the deviation of the turbulent spectrum from the power law function predicted by WTT at high frequencies — local maximum — that can be interpreted as wave energy accumulation. Our estimations show that the special case of wave turbulence is realized in our measurements, namely, discrete turbulence which is characterized by the strong influence of discreteness of cell resonant frequencies on the mechanism of the nonlinear interaction.
format Article
author Abdurakhimov, L.V.
Brazhnikov, M.Yu.
Remizov, I.A.
Levchenko, A.A.
author_facet Abdurakhimov, L.V.
Brazhnikov, M.Yu.
Remizov, I.A.
Levchenko, A.A.
author_sort Abdurakhimov, L.V.
title Classical capillary turbulence on the surface of quantum liquid He-II
title_short Classical capillary turbulence on the surface of quantum liquid He-II
title_full Classical capillary turbulence on the surface of quantum liquid He-II
title_fullStr Classical capillary turbulence on the surface of quantum liquid He-II
title_full_unstemmed Classical capillary turbulence on the surface of quantum liquid He-II
title_sort classical capillary turbulence on the surface of quantum liquid he-ii
publisher Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України
publishDate 2011
topic_facet 8th International Conference on Cryocrystals and Quantum Crystals
url http://dspace.nbuv.gov.ua/handle/123456789/118574
citation_txt Classical capillary turbulence on the surface of quantum liquid He-II / L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, A.A. Levchenko // Физика низких температур. — 2011. — Т. 37, № 5. — С. 512–516. — Бібліогр.: 21 назв. — англ.
series Физика низких температур
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fulltext © L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, and A.A. Levchenko, 2011 Fizika Nizkikh Temperatur, 2011, v. 37, No. 5, p. 512–516 Classical capillary turbulence on the surface of quantum liquid He-II L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, and A.A. Levchenko Institute of Solid State Physics RAS, Chernogolovka, Moscow district. 142432, Russia E-mail: abdurl@issp.ac.ru Received June 14, 2010 Superfluid helium-4 is a unique liquid for experimental study of capillary wave turbulence due to its very low viscosity. We have studied the influence of amplitude and spectral characteristics of the excitation force on the behavior of the turbulent cascade of capillary waves in the cylindrical cell of diameter 30 mm. We have found that the experimental results can be explained within the framework of the wave turbulence theory (WTT) when the amplitude of pumping is relatively high. However, a very interesting phenomenon was observed at moderate amplitudes of harmonic surface excitation. It was detected the deviation of the turbulent spectrum from the pow- er law function predicted by WTT at high frequencies — local maximum — that can be interpreted as wave energy accumulation. Our estimations show that the special case of wave turbulence is realized in our measure- ments, namely, discrete turbulence which is characterized by the strong influence of discreteness of cell resonant frequencies on the mechanism of the nonlinear interaction. PACS: 68.03.Kn Dynamics (capillary waves); 47.27.Gs Isotropic turbulence; homogeneous turbulence. Keywords: capillary turbulence, discrete turbulence, superfluid helium-4. Introduction Wave turbulence (WT) is a non-equilibrium state of the weakly nonlinear wave system wherein scales of energy pumping and energy dissipation are well-separated [1]. Examples of this nonlinear phenomenon can be found in diverse fields such as plasma physics, nonlinear optics, ferromagnetism, and hydrodynamics. In particular, an en- semble of nonlinear capillary waves on the liquid surface is a well-known system in which wave turbulence can be realized. For capillary waves the main processes of the nonlinear interaction are three-wave processes of decay and merging that satisfy the conservation laws of frequen- cy ω and wave-vector :k 1 2 3= ,ω +ω ω 1 2 3= .+k k k The WT theory predicts that a direct turbulent cascade is formed in the inertial range between the energy pumping scale and energy dissipation scale with the wave spectrum described by the power law function of frequency (Kolmo- gorov–Zakharov spectrum). In recent years, due to the de- velopment of technical equipment and computational tools for data processing, capillary turbulence has been in focus of experimental studies of capillary waves on the surface of water [2– 4], ethanol [4], silicon oil [5] and mercury [6]. Our previous experiments [7,8] showed that the use of quantum fluids (liquid 4He and liquid hydrogen) for inves- tigations of capillary turbulence can provide additional advantages with respect to traditional liquids due to their low viscosity. In the present paper we focus on the pecu- liarities of the shape of the turbulent wave energy distri- bution at high frequencies observed in experiments with He II, a superfluid phase of liquid 4He (preliminary results were published in [9]). For the first time we observed that under certain conditions a deviation from the power law spectrum is formed at frequencies of the order of the visc- ous cut-off scale. We also suggest a qualitative model of this phenomenon that takes into account the influence of discreteness arising due to the finite sizes of the experi- mental cell. Experimental set-up In the reported experiments with superfluid 4He we used the technique similar to that of our previous studies of capillary turbulence on the surface of liquid hydrogen [10]. The measurements were made at temperature T ≈ 1.7 K (for comparison, the temperature of the normal-to- superfluid state transition for liquid 4He at saturated vapor pressure is =Tλ 2.17 K). At this temperature superfluid helium has kinematic viscosity 5= 8.9 10−ν ⋅ cm2/s, densi- ty = 0.145ρ g/cm3, surface tension = 0.32σ din/cm [11]. Liquid helium was condensed into a copper cup of inner diameter = 30D mm and depth 4 mm. At the bottom of Classical capillary turbulence on the surface of quantum liquid He-II Fizika Nizkikh Temperatur, 2011, v. 37, No. 5 513 Fig. 1. Turbulent spectrum of capillary waves on He II surface (T = 1.7 K) obtained when the surface was pumped by sinusoidal force with frequency 80 Hz, amplitude of pumping voltage 11 V. Straight line corresponds to power law 2 3.7P − ω ω∼ predicted by the theory for narrow-band pumping. Dashed curve corresponds to exp ( /150)f−∼ . 100 1000 Frequency, Hz 10 12 10 10 10 8 10 6 10 4 10 2 P , ar b . u n it s f2 Fig. 2. Turbulent spectrum of capillary waves in the case of noise pumping at 90–200 Hz. Straight line corresponds to power law 2 2.8P − ω ω∼ predicted by the theory for broad-band pumping. Dashed curve corresponds to exp ( / 800)f−∼ . 100 1000 Frequency, Hz 10 11 10 9 10 7 10 5 10 3 P f2 , ar b . u n it s 10 10 4 the cup a radioactive thin plate was placed. Emitted from the plate β-electrons ionized 4He atoms which led to for- mation of positively charged ions and electrons. Between the cup and the upper electrode (a copper plate placed in vapor at a distance of 3 mm above the liquid surface) con- stant dc voltage 600U ≈ V of appropriate polarity was applied, so that the liquid surface was charged by positive ions. By applying low-frequency ac voltage with ampli- tudes from 1 up to 20 V to the cup, in addition to dc vol- tage, the capillary waves were excited on the charged sur- face. The advantage of this method of wave pumping is that the surface is excited directly by the driving force, rather than instability as in the experiments with parametr- ically excited waves [2,4,5] and not by blade-wavemakers as in [6] which probably resulted in any motion in the bulk. Oscillations of the surface were detected by measurements of the power of the laser beam reflected from the surface. The laser beam fell on the surface at sliding angle 0.15α ≈ producing an elliptic spot of size 1 mm×7 mm. Typical wavelengths of capillary waves in the experiments were smaller than the spot dimensions. The laser beam reflected from the oscillating surface was focused by the lens on a Si photodiode (Hamamatsu s3590-08). Time var- iations of the signal from the photodiode were amplified by a SR570 amplifier and then digitized by a 24-bit analogue- to-digital converter Leonardo-II [12] with discretization frequency 102.4 kHz. Amplified signal from the diode was proportional to the time variations of the reflected laser beam power ( )P t . Signal ( )P t was recorded to the hard disk into a series of 16 files of approximately 5 seconds long each. From Fast Fourier Transform (FFT) of every data file, power spectrum 2| |Pω was computed, and aver- aging was performed over all the 16 files. As it was shown in our previous works (see, for example, [8,10]) the re- flected laser beam power spectrum 2| |Pω was proportional to the spectrum of the correlation function of surface eleva- tion 2= | |Iω ωη , hence 2 2| | | | .Pω ωη∼ In the reported measurements two types of low- frequency driving force were used. In the first type expe- riments the surface was driven by a sinusoidal force with frequency pumpω that was equal to that of resonant fre- quencies of the cell. In the second type measurements driv- ing by a noise force was used. In this case the electrical noise was produced by a programmable noise generator. Results Figure 1 shows the turbulent spectrum of capillary waves 2Pω obtained in our experiments when the surface was pumped by ac voltage at frequency 80 Hz and ampli- tude 11 V. Turbulent distribution 2Pω looks similar to that observed earlier in our experiments on the surface of liquid hydrogen [7] and in our first experiments on the surface of liquid 4He [8]. The spectrum consists of equidistant har- monics: the first harmonic frequency corresponds to the pumping frequency, while other harmonics are generated due to the nonlinear interactions at frequencies multiple to the pumping frequency. In the inertial range the amplitudes of the harmonics depend on frequency as power law func- tion 2 mP − ω ω∼ with index 3.7m ≈ which is in accordance with the theoretical prediction for narrow-band pumping [13]. At frequencies of about 4 kHz the wave amplitudes were reduced significantly as a result of viscous dissipation and tended to the level of instrumental noise. Similarly, when the surface was forced by an intense noise pumping in the frequency range 90–200 Hz, power law spectrum 2 2.8P − ω ω∼ was obtained (Fig. 2). Index ∼2.8 is predicted by the theory for broad-band pumping [1], and the difference of the indices in the experiments with har- L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, and A.A. Levchenko 514 Fizika Nizkikh Temperatur, 2011, v. 37, No. 5 Fig. 3. Turbulent spectrum after reduction of pumping amplitude. Frequency of pumping 80 Hz, amplitude of pumping voltage 10 V. At frequencies of about 2.5 kHz, a local maximum is ob- served (emphasized by dashed curve). Dashed straight line cor- responds to 2 3.7P − ω ω∼ . 100 1000 Frequency, Hz 10 12 10 10 10 8 10 6 10 4 10 2 �b P f2 , ar b . u n it s Fig. 4. Turbulent spectrum in the case of pumping at pump / 2 = 34ω π Hz. Formation of a maximum at the spectrum is clearly seen on the main plot (circled) and in the insert on an enlarged scale. 1000 100 10 0.1 1 2000 10 0.1 100 1000 Frequency, Hz 10 11 10 9 10 7 10 5 10 3P f2 , ar b . u n it s 10 4 monic pumping and broad-band noise pumping is in ac- cordance with our previous experiments on liquid hydro- gen [14]. It is interesting to note, that, within a dissipative frequency range, the wave amplitudes in the turbulent spectrum generated by a harmonic force are decreased more rapidly than those in the spectrum generated by a noise force (exponential dashed curves in Figs 1, 2). When the amplitude of harmonic pumping was de- creased to 10 V, the shape of the turbulent spectrum is changed (Fig. 3). High-frequency edge of the turbulent cas- cade is shifted towards low frequencies which is in accor- dance with our previous experiments [8,15]. However a new phenomenon was observed, namely, formation of a well-pronounced local maximum in the wave amplitudes at frequencies of the order of high-frequency edge of turbulent cascade bω (shown by the dashed curve in Fig. 3). With further reduction of the pumping amplitude, the local max- imum was shifted towards low frequencies. Eventually, at very low pumping amplitudes the spectrum was consisted only of a few harmonics, and no local maximum was found. Formation of a local maximum was seen in a number of experiments with harmonic pumping. The common feature observed in the experiments was that the local maximum was formed near the high-frequency edge of the turbulent cascade although the shape of the local maximum and its exact position depended on the pumping frequency as well as on the pumping amplitude. For example, when the sur- face was pumped by the sinusoidal force at 34 Hz, the wave spectrum with a distinct local maximum was ob- tained (Fig. 4). However, the local maximum was located in the dissipation region of turbulent distribution rather than in the inertial range as is shown in Fig. 3. In the case of noise pumping, we never observed a local maximum. To illustrate this, in Fig. 5 we present a turbulent distribution obtained when the surface was pumped by a noise signal in the frequency range 60–130 Hz. The ampli- tude of pumping force was chosen so that the high- frequency edge of inertial interval was located approximate- ly at those frequencies at which it was seen in Figs. 3, 4. The spectrum differs drastically from the spectra observed in the experiments with harmonic pumping: it is continuous and the spectrum shape at high frequencies is more smooth. Discussion Formation of the local maximum can be interpreted as the wave energy accumulation at the high-frequency edge of the turbulent cascade where transition from the nonli- near wave energy transfer to viscous damping occurs. In the theoretical work [16] it is shown that viscous dissipa- tion (which leads to finiteness of the inertial range) can in principle result in the energy accumulation due to the bot- tleneck effect. However, it is not clear in which manner the dependence of formation of the local maximum on the Fig. 5. Turbulent spectrum of capillary waves in the case of noise pumping at 60–130 Hz. 100 1000 Frequency, Hz 10 4 10 11 10 9 10 7 10 5 10 3 10 P f2 , ar b . u n it s Classical capillary turbulence on the surface of quantum liquid He-II Fizika Nizkikh Temperatur, 2011, v. 37, No. 5 515 Fig. 6. When broadening of resonance δω is smaller than distance between two neighbour resonances ,Δω some harmonics are out of the resonances of surface oscillations in the experimental cell. �N –1 �N �N + 1 �� �� n��pump pumping amplitude observed in our measurements can be explained by the influence of viscous dissipation. On the other hand, it was pointed out by E. A. Kartashova [17,18] that there were peculiarities in weakly nonlinear wave inte- ractions in resonators due to discreteness of wavenumber space. Theory of discrete wave turbulence was developed later in a number of works, but of particular interest for us is the work [19] where the model of “frozen” turbulence was proposed. It follows from this model that, at small amplitudes of pumping, discreteness of wavenumber space can result in an oscillatory wave spectrum. We suppose that the local maximum is also caused by the discreteness of k -space. However, the above-mentioned work [19] con- siders the case of waves on the surface with square boun- dary, when the wavenumber k-space is two-dimensional. Otherwise, in our experiments the boundary geometry is cylindrical, surface oscillations should be described by the Bessel functions, and the wavenumber space is one- dimensional. It is known that the form of the basin boun- dary strongly affects the density of resonant wavenumbers [18]. Therefore, we performed the following alternative estimations to understand the influence of discreteness on spectrum in our experiments. We suppose that the pheno- menon is caused by the detuning of frequencies of the harmonics (shown in Figs. 1, 3, 4) and the resonant fre- quencies of the cell. For surface waves in a cylindrical re- sonator with diameter D the eigenvalues of wavenumber k are the roots of boundary condition equation 1( / 2) = 0J kD , where 1( )J x is a Bessel function of the first order. When k is large, the asymptotic form of the Bessel function can be used, and the resonance wave- numbers are equidistant with step 2 / .k DΔ ≈ π Hence, the distance between two neighbour resonance frequencies should grow with increasing frequency as 1/3 1/32 3= = .k k k D D ⎛ ⎞∂ω ∂ω π π σ Δω Δ ≈ ω⎜ ⎟∂ ∂ ρ⎝ ⎠ (1) Thus, for capillary waves the resonant frequencies are not equidistant which is in contrast to the frequencies of harmonics that are multiple to the pumping frequency pumpω (it should be mentioned, that in our experiments pump< ).Δω ω Obviously, such detuning is important at frequencies where broadening of resonance δω is smaller than the dis- tance between two neighbour resonances Δω (see Fig. 6) < 1.δω Δω (2) Resonance broadening δω can be presented as a sum of viscous broadening νδω and nonlinear broadening nlδω , = .nlνδω δω + δω (3) The viscous resonance broadening corresponds to the viscous damping [20] 2/3 2 4/3= 4 = 4 ,kν ω ρ⎛ ⎞δω ν ν ω⎜ ⎟σ⎝ ⎠ (4) and is related to characteristic time of viscous dissipation ντ as 1= .− ν νδω τ Nonlinear resonance broadening corres- ponds to nonlinear transfer of wave energy and is deter- mined from characteristic time of nonlinear interaction nlτ as 1= .nl nl −δω τ We suppose that for the case of harmonic pumping nonlinear time 1/6 nlτ ω∼ [21] and consequently 1/6.nl −δω ω∼ With increase of the amplitude of pumping A the nonlinearity should increase too, therefore it can be assumed that 1/6( ) ,nl A −δω ≈ ε ω (5) where ( )Aε is the increasing function of driving ampli- tude A. Thus, by substituting (1),(3),(4),(5) in (2), we obtain that detuning is important at frequencies where 2/3 4/3 1/6 1/3 1/3 4 ( / ) ( ) < 1. (3 / )( / ) A D −ν ρ σ ω + ε ω π σ ρ ω (6) At the high-frequency edge of inertial range bω , where damping of the turbulent cascade is observed, the nonlinear wave energy transfer is changed by viscous dissipation. Therefore, it can be assumed that the characteristic viscous time is close to the characteristic nonlinear time at bω , ( ) ( )b nl bντ ω ≈ τ ω . Thus, although function ( )Aε is un- known, it can be estimated from the condition that at the edge frequency bω the nonlinear broadening 1=nl nl −δω τ and the viscous broadening 1= − ν νδω τ are equal, ( ) ( ).b nl bνδω ω ≈ δω ω (7) L.V. Abdurakhimov, M.Yu. Brazhnikov, I.A. Remizov, and A.A. Levchenko 516 Fizika Nizkikh Temperatur, 2011, v. 37, No. 5 It follows from our estimations that, in our experiments, condition (6) is satisfied in the frequency domain near cut- off viscous frequency bω (both below and above bω , see Fig. 7). In this frequency domain the detuning of the har- monic frequencies and of the resonant frequencies becomes essential, and it determines the specific shape of turbulent distribution 2.Pω However, based upon a simple qualitative reasoning it is impossible to predict the exact shape and po- sition of the local maximum. Thus, detailed theoretical stu- dies and numerical simulations are required to understand the mechanism of formation of the local maximum. The model proposed implies that the following condi- tions should be satisfied for observation of energy accumu- lation in the case of capillary turbulence: low viscous broadening (low viscosity of liquid), low nonlinear broa- dening (harmonic pumping with a moderate amplitude), and large distance between the resonant frequencies (a relatively small size of the cell). In our experiments these conditions were fulfilled. It is interesting to note that the use of superfluid 4He allowed us to observe the energy accumulation in turbulent cascade due to its very low vis- cosity in comparison with classical liquids. We are grateful to L.P. Mezhov-Deglin, G.V. Kolma- kov, E.A. Kuznetsov for fruitful discussions and A.V. Lokhov for experimental assistance. The work was sup- ported by RFBR grants 09-02-01146, 07-02-00728 and the programs of the Presidium RAS “Quantum Physics of Condensed Matter” and “Fundamental Problems of Nonli- near Dynamics”. 1. V. Zakharov, V. Lvov, and G. Falkovich, Kolmogorov Spectra of Turbulence, Vol. 1, Springer, Berlin (1992). 2. W.B. Wright, R. Budakian, S.J. Putterman, Phys. Rev. Lett. 76, 4528 (1996); E. Henry, Р. Аlstrom, and M.T. Levinsen, Europhys. Lett. 52, 27 (2000); H. Punzmann, M.G. Shats, and H. Xia, Phys. Rev. Lett. 103, 064502 (2009). 3. M.Yu. Brazhnikov, G.V. Kolmakov, A.A. Levchenko and L.P. Mezhov-Deglin, Europhys. Lett. 58, 510 (2002). 4. C. Falcon, E. Falcon, U. Bortolozzo, and S. Fauve, Europhys. Lett. 86, 14002 (2009). 5. Mark-Tiele Westra, Patterns and Weak Turbulence in Surface Waves, ISBN 90-386-1749-6, Eindhoven (2001). 6. E. Falcon, C. Laroche, and S. Fauve, Phys. Rev. Lett. 98, 094503 (2007). 7. L.V. Abdurakhimov, M.Yu. Brazhnikov, and A.A. Levchenko, JETP Lett. 89, 120 (2009); L.V. Abdurakhimov, M.Yu. Brazhnikov, and A.A. Levchenko, JETP Lett. 88, 19 (2008); G.V. Kolmakov, M.Y. Brazhnikov, A.A. Levchenko, L.V. Abdurakhimov, P.V.E. McClintock, and L.P. Mezhov- Deglin, in: Progress in Low Temperature Physics, Quantum Turbulence, Elsevier, Oxford (2009), Vol. XVI, p. 306. 8. L.V. Abdurakhimov, M.Yu. Brazhnikov, and A.A. Levchenko, Fiz. Nizk. Temp. 35, 127 (2009) [Low Temp. Phys. 35, 95 (2009)]. 9. L.V. Abdurakhimov, M.Yu. Brazhnikov, G.V. Kolmakov, and A.A. Levchenko, J. Phys.: Conf. Series 150, 032001 (2009). 10. M.Yu. Brazhnikov, A.A. Levchenko, and L.P. Mezhov- Deglin, Instruments Exp. Techn. 45, 758 (2002). 11. R.J. Donnelly and C.F. Barenghi, J. Phys. Chem. Ref. Data 27, 1217, URL http://darkwing.uoregon.edu/∼ rjd/vapor1.htm (1998). 12. http://www.rudshel.ru/pdf/Leonardo-II.rar 13. G.E. Falkovich and A.V. Shafarenko, Sov. Phys. JETP 67, 1393 (1988). 14. M.Yu. Brazhnikov, G.V. Kolmakov, and A.A. Levchenko, JETP 122, 521 (2002). 15. M.Yu. Brazhnikov, G.V. Kolmakov, A.A. Levchenko, and L.P. Mezhov-Deglin, JETP Lett. 74, 583 (2001). 16. I.V. Ryzhenkova and G.E. Falkovich, Sov. Phys. JETP 71, 1085 (1990). 17. E.A. Kartashova, Physica D46, 43 (1990). 18. E.A. Kartashova, Physica D54, 125 (1991). 19. A.N. Pushkarev and V.E. Zakharov, Physica D135, 98 (2000). 20. L.D. Landau and E.M. Lifshitz, Fluid Mechanics, Course of Theoretical Physics, Pergamon Press (1987) Vol. 6. 21. G.V. Kolmakov, JETP Lett. 83 (2), 58 (2006). Fig. 7. Results of estimation of relative broadening /δω Δω . Ascending thin curve represents viscous relative broadening /νδω Δω , descending thin curve —nonlinear relative broadening /nlδω Δω , thick curve with minimum — total relative broaden- ing /δω Δω . 1.5 1 0.5 10 100 1000 10 4 R el at iv e b ro ad en in g Frequency, Hz