Temperature-dependent bulk viscosity of nitrogen gas determined from spontaneous Rayleigh–Brillouin scattering

Gu, Ziyu; Ubachs, Wim

doi:10.1364/ol.38.001110

Cited by 52 publications

(71 citation statements)

References 16 publications

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“…Since it follows from previous studies, that the bulk viscosity exhibits a linearly increasing trend with the temperature 30,31 , as it is expected from theoretical considerations 42 , values of the bulk viscosity are derived for the different temperature settings for the experiments, for the three different gases. The thus obtained values for the derived bulk viscosities for air, N 2 and O 2 as a function of temperature (for further discussion see below) are employed to interpolate the values for the other settings in p − T parameter space as listed in Table II.…”

Section: Measurements and Analysismentioning

confidence: 91%

A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

Ubachs

2014

The Journal of Chemical Physics

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Spontaneous Rayleigh-Brillouin scattering experiments in air, N 2 and O 2 have been performed for a wide range of temperatures and pressures at a wavelength of 403 nm and at a 90 degrees scattering angle. Measurements of the Rayleigh-Brillouin spectral scattering profile were conducted at high signal-to-noise ratio for all three species, yielding high-quality spectra unambiguously showing the small differences between scattering in air, and its constituents N 2 and O 2 . Comparison of the experimental spectra with calculations using the Tenti S6 model, developed in 1970s based on linearized kinetic equations for molecular gases, demonstrates that this model is valid to high accuracy for N 2 and O 2 , as well as for air. After previous measurements performed at 366 nm, the Tenti S6 model is here verified for a second wavelength of 403 nm, and for the pressuretemperature parameter space covered in the present study (250 -340 K and 0.6 -3 bar). In the application of the Tenti S6 model, based on the transport coefficients of the gases, such as thermal conductivity κ, internal specific heat capacity c int and shear viscosity η as well as their temperature dependencies taken as inputs, values for the more elusive bulk viscosity η b for the gases are derived by optimizing the model to the measurements. It is verified that the bulk viscosity parameters obtained from previous experiments at 366 nm, are valid for wavelengths of 403 nm. Also for air, which is treated as a single-component gas with effective gas transport coefficients, the Tenti S6 treatment is validated for 403 nm as for the previously used wavelength of 366 nm, yielding an accurate model description of the scattering profiles for a range of temperatures and pressures, including those of relevance for atmospheric studies. It is concluded that the Tenti S6 model, further verified in the present study, is applicable to LIDAR applications for exploring the wind velocity and the temperature profile distributions of the Earth's atmosphere. Based on the present findings at 90• scattering and the determination of η b values predictions can be made on the spectral profiles for a typical LIDAR backscatter geometry. These Tenti S6 predictions for Rayleigh-Brillouin scattering deviate by some 7% from purely Gaussian profiles at realistic sub-atmospheric pressures occurring at 3-5 km altitude in the Earth's atmosphere.

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Section: Measurements and Analysismentioning

confidence: 91%

A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

Ubachs

2014

The Journal of Chemical Physics

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“…Experimentally, the bulk viscosity is obtained by comparing the experimental spectra with those from the s6 model (Vieitez et al 2010;Gu & Ubachs 2013). If the viscosity index of the gas is 0.5, some errors will be introduced.…”

Section: Spontaneous Rayleigh-brillouin Scatteringmentioning

confidence: 99%

“…Further numerical simulations show that the closer the viscosity index is to one, the smaller the error that is introduced when comparing experimental spontaneous RBS spectra with those of the s6 model. Figure 8 compares the spontaneous RBS spectra of nitrogen produced by our model with the experimental data of Gu & Ubachs (2013). The experimental spectrum is the convolution of the spectrum S and the instrumental spectral response function, which can be found in Vieitez et al (2010).…”

Section: Spontaneous Rayleigh-brillouin Scatteringmentioning

confidence: 99%

A kinetic model of the Boltzmann equation for non-vibrating polyatomic gases

White

Scanlon

et al. 2014

J. Fluid Mech.

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A kinetic model of the Boltzmann equation for non-vibrating polyatomic gases is proposed, based on the Rykov model for diatomic gases. We adopt two velocity distribution functions (VDFs) to describe the system state; inelastic collisions are the same as in the Rykov model, but elastic collisions are modelled by the Boltzmann collision operator (BCO) for monatomic gases, so that the overall kinetic model equation reduces to the Boltzmann equation for monatomic gases in the limit of no translational-rotational energy exchange. The free parameters in the model are determined by comparing the transport coefficients, obtained by a Chapman-Enskog expansion, to values from experiment and kinetic theory. The kinetic model equations are solved numerically using the fast spectral method for elastic collision operators and the discrete velocity method for inelastic ones. The numerical results for normal shock waves and planar Fourier/Couette flows are in good agreement with both conventional direct simulation Monte Carlo (DSMC) results and experimental data. Poiseuille and thermal creep flows of polyatomic gases between two parallel plates are also investigated. Finally, we find that the spectra of both spontaneous and coherent Rayleigh-Brillouin scattering (RBS) compare well with DSMC results, and the computational speed of our model is approximately 300 times faster. Compared to the Rykov model, our model greatly improves prediction accuracy, and reveals the significant influence of molecular models. For coherent RBS, we find that the Rykov model could overpredict the bulk viscosity by a factor of two.

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“…This information can be extracted by comparing the experimental and theoretical spectra, where the accuracy of the obtained information depends on how reliable the experimental and theoretical results are. In the past few years, rapid improvements in the experimental resolution have been achieved [1,2,3], however, accurate theoretical line shapes (spectra) are lacking, although several kinetic models have been proposed [4,5,6,7].…”

Section: Introductionmentioning

confidence: 99%

“…Accurate theoretical line shapes are difficult to obtain in the kinetic regime 0.05 < Kn < 1, as the intricate Boltzmann equation (BE) must be solved. However, this regime is of significant interest since the line shape is sensitive to gas states, which allows accurate measurement of gas properties including the bulk viscosity [2].…”

Section: Introductionmentioning

confidence: 99%

Preface: 29th International Symposium on Rarefied Gas Dynamics

Fan¹

2014

AIP Conference Proceedings

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Abstract. The spectrum of the coherent Rayleigh-Brillouin scattering (CRBS) of light by a rarefied gas is obtained by solving the Boltzmann equation numerically using the fast spectral method. The influence of the intermolecular potential on the CRBS spectrum is investigated and the accuracy of the prevailing Tenti's s6 kinetic model is evaluated. Our numerical results show that i) the intermolecular potential has a great influence on CRBS spectrum when the Knudsen number is between 0.05 and 1 and ii) Tenti's s6 kinetic model can only predict the line shape accurately for Maxwell gases at small Knudsen numbers.

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Temperature-dependent bulk viscosity of nitrogen gas determined from spontaneous Rayleigh–Brillouin scattering

Cited by 52 publications

References 16 publications

A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

A systematic study of Rayleigh-Brillouin scattering in air, N2, and O2 gases

A kinetic model of the Boltzmann equation for non-vibrating polyatomic gases

Preface: 29th International Symposium on Rarefied Gas Dynamics

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