Gas velocimetry based on infrared laser-induced fluorescence

Song, Zuwei; Wang, Weitian; Zhu, Ning; Chao, Xing

doi:10.1063/5.0074367

Cited by 4 publications

(1 citation statement)

References 33 publications

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“…The OPO system outputs both wavelengths with a total maximum pulse energy of 17 mJ, and only the 2.0 µm laser output is used to excite the 2v 1 + v 3 band of CO 2 . The CO 2 absorption cross section at this excited wavelength has been measured to be 4.5 × 10 −22 cm 2 [34]. As for the probe laser, a continuous-wave diode-pumped solid-state laser at 671 nm with maximum output power of 2 W (MRL-N-671 nm-2 W, CNI Tech.…”

Section: Methodsmentioning

confidence: 99%

Directly-excited laser-induced thermal grating spectroscopy and thermometry with carbon dioxide vibrational transition

Song,

Zhu,

Wang

et al. 2024

Meas. Sci. Technol.

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Laser-induced thermal grating spectroscopy (LITGS) has been proved for accurate thermometry and measurement of energy transfer processes in molecules. While electronic transitions are often used for excitation in previous LITGS works, here we report laser-induced thermal gratings formed by direct excitation of CO2 with an infrared (IR) laser at wavelength near 2 μm, with which high signal-to-noise ratio LITGS signals are generated (SNR ∼ 300 at room temperature). A theoretical LITGS model assuming a ‘two-steps’ energy transfer process is used to describe the recorded signal waveform, with relative fitting residuals of less than 10%. Quantitative thermometry is performed in CO2 gas flows between 293 K and 420 K, with a relative uncertainty of 1.6% and a precision of 1.1% defined as the 1-σ standard deviation of 30 repeated measurement. Furthermore, the time constants of vibrational energy transfer at different temperatures are extracted from the temporal signal waveform with a precision better than 80 ns, and the measured results are consistent with the simulation using a detailed vibrational energy transfer model. These results demonstrate IR LITGS as a potential tool for spatially-resolved measurement of the thermophysical properties of fluids, as well as molecular vibrational energy transfer processes.

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Section: Methodsmentioning

confidence: 99%

Directly-excited laser-induced thermal grating spectroscopy and thermometry with carbon dioxide vibrational transition

Song,

Zhu,

Wang

et al. 2024

Meas. Sci. Technol.

Self Cite

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Spectra and structure functions of the temperature and velocity fields in supergravitational thermal turbulence

et al. 2022

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We analyse the power spectra and structure functions (SFs) of the temperature and radial velocity fields, calculated in the radial and azimuthal directions, in annular centrifugal Rayleigh-B\'{e}nard convection (ACRBC) for Rayleigh number Ra $ \in [{10^8},{10^{11}}]$, Prandtl number Pr = 10.7, and inverse Rossby number $\rm{Ro}^{-1} = 16$ using the spatial data obtained by quasi-two-dimensional direct numerical simulation. Bolgiano and Obukhov-like (BO59-like) scalings for the energy spectrum in both the azimuthal and radial directions and thermal spectrum in the azimuthal direction are observed. The range of BO59-like scaling becomes wider as Ra increases. At $\rm{Ra} = 10^{11}$, it is found that BO59-like scaling ${E_u}({k_r}) \sim {k_r}^{ - 11/5}$ spans nearly two decades for the energy spectrum calculated in the radial direction. Power-law fittings in the range larger than the Bolgiano scales, the scaling exponents of transverse and longitudinal velocity SFs versus the order coincide with the theoretical prediction of BO59 scaling $\zeta _p^u = 3p/5$ basically. The second-order temperature SFs exhibit a gradual transition from the Obukhov-Corrsin behaviour at scales smaller than the Bolgiano scales to the BO59 behaviour at scales larger than the Bolgiano scales. The slopes from the 3rd to 6th-order temperature SFs are similar, which is similar to classical Rayleigh-B\'{e}nard convection and Rayleigh-Taylor turbulence. The probability density functions (p.d.f.) of temperature fluctuations $\delta T/{\sigma _T}$ reveal the cold plumes are strong and the p.d.f. in different regions at high Ra are similar. The stronger turbulent-mixing and larger centrifugal buoyancy in ACRBC may result in the BO59-like scaling.

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