Influence of Mie and Geometric Scattering Contributions on Temperature and Density Measurements in Filtered Rayleigh Scattering

Boyda, Matthew T.; Byun, Gwibo; Saltzman, Ashley J.; Lowe, K. Todd

doi:10.2514/6.2020-1516

Cited by 4 publications

(6 citation statements)

References 14 publications

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“…In cases where this is not possible, other strategies must be adopted since Mie scattering interference can introduce bias errors in FRS property measurements. Recently Boyda et al introduced a method to account for Mie scattering by estimating its spectrum as a Normal distribution with a width determined by the turbulence intensity of the flow [42,43].…”

Section: Theory Of the Typical Frs Experimentsmentioning

confidence: 99%

“…Only geometric scattering is depicted here (blue shaded region). If Mie scattering existed, its contribution would be Doppler-shifted the same amount as the Rayleigh contribution, but its spectral width would be much narrower [43].…”

Section: Theory Of the Typical Frs Experimentsmentioning

confidence: 99%

“…Citing these issues, some researchers have used continuous wave (CW) lasers, like diode-pumped solid state frequencydoubled Nd:YVO 4 lasers, to provide 532 nm illumination with linewidths less than 5 MHz at powers up to 18 W [42,43,50,[67][68][69][70]. These spectrally pure illumination sources have enabled measurements in challenging internal flow environments with a large amount of background scattering.…”

Section: Lasermentioning

confidence: 99%

“…In fact, it is now generally accepted that modern CMOS cameras are equally as suitable as their CCD counterparts for many scientific applications [89,98]. CMOS cameras have been used for FRS measurements by Boyda et al [43] and will likely continue to be adopted as scientific CMOS cameras continue to develop and high speed FRS continues to be pursued.…”

Section: Detectormentioning

confidence: 99%

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Quantitative gas property measurements by filtered Rayleigh scattering: a review

Ground¹,

Hunt²,

Hunt³

2023

Meas. Sci. Technol.

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Filtered Rayleigh scattering (FRS) is a laser-based diagnostic technique used to nonintrusively quantify various thermodynamic properties of a light-scattering gas. The backbone of FRS is the molecular filtering of Rayleigh scattered light. This concept was initially introduced by the atmospheric LIDAR community before being adopted within the aerospace research field in the early 1990s. Since then, FRS has matured into a versatile quantitative diagnostic tool and has found use in a variety of flow regimes ranging from sub- to supersonic speeds in both reacting and nonreacting environments. This adoption can be attributed to the wealth of information that can be obtained via FRS, including the gas density, pressure, temperature, velocity, species composition, or, in some cases, several of these properties at once. This article reviews the current state of FRS methodology in recovering such gas properties. As knowledge of the fundamentals of Rayleigh scattering and spectral light filtering is crucial to the design of an FRS experiment, we begin by briefly reviewing these areas. Subsequently, we conduct a survey of experimental design strategies, assumptions, and data reduction methods used to measure different gas properties using FRS. We conclude the review with a short discussion on quantification of experimental uncertainty and future trends in FRS.

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Section: Theory Of the Typical Frs Experimentsmentioning

confidence: 99%

Section: Theory Of the Typical Frs Experimentsmentioning

confidence: 99%

Section: Lasermentioning

confidence: 99%

Section: Detectormentioning

confidence: 99%

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Quantitative gas property measurements by filtered Rayleigh scattering: a review

Ground¹,

Hunt²,

Hunt³

2023

Meas. Sci. Technol.

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“…Boyda et al [28] describe that the actual signal received by the measurement device (camera) is the convolution of the transmission spectrum of the molecular filter and the Rayleigh, Mie, and background (geometric) scattering spectrum. This can be seen in Eq.…”

Section: Convolution Modeling Of Rayleigh Scattering and Iodine Trans...mentioning

confidence: 99%

Auto-Processing of Filtered Rayleigh Scattering Images Including Mie and Background Scattering Contributions

Powers

Byun

Lowe

2022

Preprint

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A comprehensive and efficient post-processing framework is presented for obtaining aerodynamics measurements of three-component velocity, static temperature, and static density using filtered Rayleigh scattering (FRS). This framework contains several steps which culminate in an optimization process for iterative minimization of errors between the experimentally measured FRS spectra and spectra generated by models, providing an inverse solution to determine the local measurement values. Robustness is gained using a multi-level processing technique for successive spatial resolution refinement of measurements. An assessment of the speed and spectral outputs of several published laser Rayleigh scattering models is provided and resulted in the recommendation that Doll's analytic Tenti-S6 model be adopted as the best trade-off in speed and consistency. A distinguishing feature of the approach is the inclusion of methods for interpreting FRS spectra that contain significant scattering contributions from particles and surfaces. The performance of the methods has been quantified for uncertainties using Monte Carlo simulations, while planar results from two experiments are presented for validation and demonstration of robustness, respectively: a benchtop free jet and the exhaust plume of a miniature turbojet engine. Monte Carlo simulations show that at a signal-to-noise ratio (SNR) of 30 dB the approximate uncertainty in scattering angle is 0.3°, 2.5 K for static temperature, 1.5 m/s for velocity, 0.01 kg/m3 for static density, and 0.01 for both Mie and background scattering intensity ratios. The free jet results show differences of 1.5 K for total temperature, 1 m/s for axial velocity, 0.005 kg/m3 for total density, and 200 Pa for total pressure when compared to probe data. All results fall within the 95% confidence bounds of the a priori uncertainties. The small turbojet (JetCat) results are included to show that the processor is robust and accurate even when used with non-ideal data sets from realistic applications such as vitiated exhausts. The JetCat results show differences of 20 K for total temperature, 8 m/s for axial velocity, 0.01 kg/m3 for total density, and 500 Pa for total pressure when compared to probe data. All results except near the edge of the jet plume fall within the 95% confidence bounds of the a priori uncertainties.

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Validation of Filtered Rayleigh Scattering Optical Rake Measurement Techniques in Turbomachinery Applications and Boundary Layers

Powers,

Byun,

Lowe

2023

Journal of Turbomachinery

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Filtered Rayleigh scattering (FRS) is a non-intrusive, laser-based optical technique for measuring 3-component velocity, static temperature, and static density with high spatial resolution and low uncertainty. FRS can be used to derive total values as well as turbomachinery efficiencies. The Virginia Tech team has been developing this seedless technique for simultaneous planar (or line) measurements to overcome the limitations associated with seed-based laser measurement techniques such as laser Doppler velocimetry (LDV), particle image velocimetry (PIV), and Doppler global velocimetry (DGV) as well as limitations with physical probe rakes such as blockage and wake production. This technique is especially attractive in flow cases or environments where the aforementioned seed-based laser measurement techniques are limited or not possible. A combination of specially designed boundary layer total pressure probe rake measurements, FRS optical rake measurements, and computational fluid dynamics (CFD) results in the inlet of a Honeywell TFE731-2 turbofan are presented. Results show that all three techniques (FRS, probe, and CFD) match within approximately 2% root-mean-square error (RMSE). Inlet efficiency was derived and found to be within 2.3% difference for all three techniques.

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Influence of Mie and Geometric Scattering Contributions on Temperature and Density Measurements in Filtered Rayleigh Scattering

Cited by 4 publications

References 14 publications

Quantitative gas property measurements by filtered Rayleigh scattering: a review

Quantitative gas property measurements by filtered Rayleigh scattering: a review

Auto-Processing of Filtered Rayleigh Scattering Images Including Mie and Background Scattering Contributions

Validation of Filtered Rayleigh Scattering Optical Rake Measurement Techniques in Turbomachinery Applications and Boundary Layers

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