Flow Visualization at Cryogenic Conditions Using a Modified Pressure Sensitive Paint Approach

Watkins, A. Neal; Goad, W. K.; Obara, Clifford J.; Sprinkle, Danny R.; Campbell, Richard L.; Carter, Melissa B.; Pendergraft, Odis C.; Bell, James H.; Ingram, JoAnne L.; Oglesby, Donald M.

doi:10.2514/6.2005-456

Cited by 8 publications

(5 citation statements)

References 14 publications

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“…For initial application of direct excitation and detection of singlet oxygen we will focus on its potential use in cryogenic wind tunnel testing. 26,27 We plan to develop a novel method for obtaining quantitative non-intrusive mapping of the 2-D oxygen/pressure at many points. The image intensity of the 1270 nm luminescence should generate a map whose intensities are proportional to the oxygen concentration which is directly proportional to pressure.…”

Section: Discussionmentioning

confidence: 99%

Singlet molecular oxygen by direct excitation

Jockusch

Turro

Thompson

et al. 2008

Photochem Photobiol Sci

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Direct excitation at 1064 nm and detection of singlet molecular oxygen at 1270 nm is made possible by the availability of powerful YAG-lasers and sensitive NIR photomultipliers. Singlet oxygen was generated in condensed phase at 77 K by direct excitation at 1064 nm (without the use of sensitizers). Several luminescing species were observed by time resolved luminescence spectroscopy and luminescence lifetime measurements, including the single molecule (1)Delta(g)and (1)Sigma(g)(+)states as well as luminescence from the [(1)Delta(g)](2) simultaneous transition. As an application we propose a novel method for obtaining quantitative non-intrusive mapping of the 2-D oxygen concentrations and pressure at cryogenic temperatures, which is of importance in aircraft design for high altitudes.

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Section: Discussionmentioning

confidence: 99%

Singlet molecular oxygen by direct excitation

Jockusch

Turro

Thompson

et al. 2008

Photochem Photobiol Sci

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“…Surface visualization techniques have found varying degrees of success to date in high pressure, cryogenic wind tunnels. Temperature sensitive paint [6,7], Moiré interferometry [8], and photogrammetry [9] have been used successfully for qualitative and quantitative flow and aerodynamic surface measurements, while the pressure sensitive paint technique has only achieved limited qualitative success [10][11][12], though modern signal-lifetime-based variants have shown more promise [12]. Techniques sensitive to density, such as shadowgraphy, schlieren, and variants [14,15] as well as Rayleigh scattering [16][17][18], have shown some utility at qualitative and quantitative off-body measurements.…”

Section: Introductionmentioning

confidence: 99%

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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“…Measurement techniques such as photogrammetry [5,6] and Moiré interferometry [7] have been successfully applied in the National Transonic Facility (NTF) and the European Transonic Windtunnel (ETW) to provide aeroelastic deformation measurements on a variety of different models. On-body surface pressures and temperatures have been measured using cryogenic pressure-and temperature-sensitive paints [8][9][10][11][12]. In the NTF, flow disturbance measurements were made using a survey rake containing various temperature, velocity, and pressure probes; however, the cryogenic environment was found to negatively impact the survivability and repair of hot wire probes [13].…”

Section: Introductionmentioning

confidence: 99%

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

Reese

Jiang

Danehy

2020

Meas. Sci. Technol.

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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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Flow Visualization at Cryogenic Conditions Using a Modified Pressure Sensitive Paint Approach

Cited by 8 publications

References 14 publications

Singlet molecular oxygen by direct excitation

Singlet molecular oxygen by direct excitation

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

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