Femtosecond Laser Electronic Excitation Tagging Velocimetry in a Transonic, Cryogenic Wind Tunnel

Burns, Ross A.; Danehy, Paul M.; Halls, Benjamin R.; Jiang, Naibo

doi:10.2514/1.j055325

Cited by 22 publications

(15 citation statements)

References 8 publications

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“…The data take this form because of the boresight imaging configuration; a greater degree of elongation corresponds to a larger angle between the laser beam propagation direction and the imaging line of sight. Unlike the FLEET data taken in preliminary tests [35], which showed a nearly axisymmetric intensity distribution, the FLEET data are much more ragged in appearance and lack radial symmetry.…”

Section: Fleet Signal Processingcontrasting

confidence: 66%

“…The position of the FLEET signal within each image was then precisely located utilizing a custom surface fitting algorithm, the shifted, rotated, generic ellipsoid (SRGE) algorithm [38]. This surface fitting technique fits a generic ellipsoidal function to the data, which allows for polar variations in the intensity distribution not afforded by simple Gaussian or bi-Gaussian fits [35]. The mathematical details of this fitting algorithm can be found in [38].…”

Section: Fleet Signal Processingmentioning

confidence: 99%

“…Consequently, it could be possible to make velocity measurements with a much broader dynamic range. To date, initial viability tests were performed and reported by the authors [35]. While these initial tests proved successful, the conditions over which they were conducted were limited to elevated temperatures and suffered from poor measurement precision across all conditions.…”

Section: Introductionmentioning

confidence: 99%

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Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part I. Femtosecond-laser tagging

Burns

Peters

Danehy

2018

Meas. Sci. Technol.

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Femtosecond laser electronic excitation tagging (FLEET) velocimetry is characterized for the first time at high-pressure, low-temperature conditions. FLEET signal intensity and signal lifetime data are examined for their thermodynamic dependences; temperatures range from 89 K to 275 K while pressures are varied from 85 kPa to 400 kPa. The FLEET signal intensity is found to scale linearly with the flow density. An inverse density dependence is observed in the FLEET signal lifetime data, with little independent sensitivity to the other thermodynamic conditions apparent. FLEET velocimetry is demonstrated in the NASA Langley 0.3 m Transonic Cryogenic Tunnel. Velocity measurements are made over the entire operational envelope: Mach numbers from 0.2 to 0.75, total (stagnation) temperatures from 100 K to 280 K, and total pressures from 100 kPa to 400 kPa. The velocity measurement accuracy is assessed over this domain of conditions. Measurement errors below 1.15 % are typical, with slightly decreasing accuracy as temperatures are decreased. Assessment of the measurement precision finds a zero-velocity precision of 0.4 m s−1. The precision is observed to have a weak temperature dependence as well, likely a result of the shorter lifetimes experienced at higher densities. The velocity dynamic range is found to have a nominal value of 650. Finally the spatial resolution of the measurements is found to be dominated by the physical size of the FLEET signal and advective motion. The transverse spatial resolution is found to be 1 mm, the spanwise spatial resolution to be 2–3 mm, while the streamwise spatial resolution is dependent on velocity with a minimum of 2 mm and a maximum of 3.3 mm.

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Section: Fleet Signal Processingcontrasting

confidence: 66%

Section: Fleet Signal Processingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part I. Femtosecond-laser tagging

Burns

Peters

Danehy

2018

Meas. Sci. Technol.

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“…When presented as a percentage, the standard error represents the average percent error of all velocity measurements included in the calculation. Standard error was found to be 1.6%, which is consistent with previous FLEET and PLEET measurements in the 0.3 m TCT that found the accuracy to lie between 0.6% and 2.1% [28,30,42]. This standard error also shows that the STARFLEET method not only performs roughly as well as laser Doppler velocimetry in the 0.3 m TCT (which obtained typical velocity measurement error less than 1% [22]), but does so more consistently and over a broader range of conditions.…”

Section: Velocity Measurement Accuracysupporting

confidence: 89%

Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part III. Resonant femtosecond-laser tagging

Reese

Jiang

Danehy

2020

Meas. Sci. Technol.

Self Cite

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Selective two-photon absorptive resonance femtosecond laser electronic excitation tagging (STARFLEET) velocimetry is characterized for the first time at high-pressure, low-temperature conditions. Studies were carried out in the NASA Langley Research Center's 0.3 meter transonic, cryogenic wind tunnel, with flow conditions spanning the entire operational envelope of the facility; total pressures ranging from 100 kPa to 517 kPa, total temperatures from 80 K to 327 K, and Mach numbers from 0.2 to 0.85. STARFLEET signal intensity and lifetime measurements are examined for their thermodynamic dependencies since both intensity and lifetime have implications for measurement precision. Signal intensity is found to be inversely proportional to density, while lifetime scales nearly linearly with density until approaching the liquid-vapor saturation point of nitrogen. The velocity measurement accuracy and precision are assessed over the full domain of conditions, and standard error was determined to be 1.6%, while precision ranged from roughly 1.5% to 10% of the freestream velocity. The precision was also observed to have a temperature dependence, likely a result of the longer lifetimes experienced at higher densities.

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“…The incident 100 fs laser dissociates the nitrogen molecules into atoms, which subsequently recombine into the excited B state of molecular nitrogen, which emits in the red and near infrared through the first positive transition to the A state. FLEET is used in a wide range of applications, including subsonic [134,[139][140][141], transonic [136,[142][143][144], and hypersonic [145][146][147][148] flow fields. At present, FLEET has been successfully applied in nitrogen [134,140,141,[149][150][151][152], argon [139,[153][154][155], air [141,147,156,157], 1,1,1,2-Tetrafluoroethane [158], helium [159], carbon dioxide [159], oxygen [159], and combustion [141,148,160] flow fields.…”

Section: Tagging Velocimetry Based On Femtosecond Laser-induced Emissionmentioning

confidence: 99%

A Review of Femtosecond Laser-Induced Emission Techniques for Combustion and Flow Field Diagnostics

Zhang

Liu

et al. 2019

Applied Sciences

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The applications of femtosecond lasers to the diagnostics of combustion and flow field have recently attracted increasing interest. Many novel spectroscopic methods have been developed in obtaining non-intrusive measurements of temperature, velocity, and species concentrations with unprecedented possibilities. In this paper, several applications of femtosecond-laser-based incoherent techniques in the field of combustion diagnostics were reviewed, including two-photon femtosecond laser-induced fluorescence (fs-TPLIF), femtosecond laser-induced breakdown spectroscopy (fs-LIBS), filament-induced nonlinear spectroscopy (FINS), femtosecond laser-induced plasma spectroscopy (FLIPS), femtosecond laser electronic excitation tagging velocimetry (FLEET), femtosecond laser-induced cyano chemiluminescence (FLICC), and filamentary anemometry using femtosecond laser-extended electric discharge (FALED). Furthermore, prospects of the femtosecond-laser-based combustion diagnostic techniques in the future were analyzed and discussed to provide a reference for the relevant researchers.

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Femtosecond Laser Electronic Excitation Tagging Velocimetry in a Transonic, Cryogenic Wind Tunnel

Cited by 22 publications

References 8 publications

Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part I. Femtosecond-laser tagging

Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part I. Femtosecond-laser tagging

Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part III. Resonant femtosecond-laser tagging

A Review of Femtosecond Laser-Induced Emission Techniques for Combustion and Flow Field Diagnostics

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