Air photolysis and recombination tracking - A new molecular tagging velocimetry scheme

Sijtsema, N. M.; Dam, N. J.; Klein-Douwel, R. J. H.; Meulen, J. ter

doi:10.2514/3.15163

Cited by 2 publications

(2 citation statements)

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“…Its advantage over PIV techniques in high-speed facilities is that it is not limited by timing issues associated with tracer injection [12] or reduced particle response at Knudsen and Reynolds numbers [4] characteristic of high-speed wind tunnels. Methods of tagging velocimetry include the VENOM [13][14][15][16][17], APART [18][19][20], RELIEF [21][22][23][24][25], FLEET [26,27], STARFLEET [28], PLEET [29], NO [30][31][32][33][34], argon [35], iodine [36,37], sodium [38], acetone [39][40][41], NH [42], and the hydroxyl group techniques [43][44][45][46], among others [47][48][49][50][51][52].…”

Section: Introductionmentioning

confidence: 99%

Single-Laser Krypton Tagging Velocimetry Investigation of Supersonic Air and N2 Boundary-Layer Flows over a Hollow Cylinder in a Shock Tube

2019

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In this paper, we investigate the boundary-layer profiles that form over a sharp, hollow cylinder in supersonic air and N 2 flows with a krypton tagging velocimetry (KTV) single-laser scheme. The supersonic flows are generated by the passage of the primary shock wave over the model in the Stevens shock tube. The experiments are performed in two gas mixtures doped with Kr: 99% N 2 /1% Kr, to model N 2 , and 75% N 2 /20% O 2 /5% Kr, to model air. The experimental setup allows us to vary the pressure and Reynolds number from 3-25 kPa and 1.5 × 10 5 to 1.5 × 10 6 m −1 , respectively, while the Mach number is kept fixed at 1.7. The static temperature and pressure (but not the velocity) are representative of typical large-scale high-enthalpy hypersonic impulse facilities. The KTV data points over the hollow cylinder are mapped to corresponding wall-normal locations above a flat plate, which enables comparison with the similarity solution for compressible boundary-layer flow. Agreement between the similarity solution and experimental results is excellent. Relative to previous two-laser KTV schemes, the single-laser approach used in this work has the advantage of being simpler and more cost effective, but it has a higher laserenergy requirement, 10 mJ/pulse in these experiments. Single-laser KTV is implemented by increasing the energy of the write-laser pulse to a sufficient level such that the Kr becomes partially ionized via a (2 + 1) resonance-enhanced, multiphoton ionization (REMPI) process with an excitation wavelength of 212.6 nm. The write step records the fluorescence that results primarily from the spontaneous emission from the two-photon excitation. After a prescribed delay, the read step records the fluorescence that results from the transitions that follow the recombination process. The signal-to-noise ratio (SNR) is sufficient to extract velocity profiles from single-shot, shock-tube experiments. Two-photon absorption cross-section calculations and emission spectra are presented to justify the chosen excitation wavelength and support our understanding of the Kr excitation and emission scheme.

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Section: Introductionmentioning

confidence: 99%

Single-Laser Krypton Tagging Velocimetry Investigation of Supersonic Air and N2 Boundary-Layer Flows over a Hollow Cylinder in a Shock Tube

2019

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“…This technique, dubbed air photolysis and recom bination tracking (APART), involves locally creating a line of nitric oxide molecules out of ambient nitrogen and oxygen, using a weakly focused excimer laser beam at 193 nm [16]. In a previous Letter [17], it was shown that the N O production yield scales linearly with the intensity of N j fluorescence (k = 391 nm, B2R j ! X2R j (0,0)) that also originates from the laser focus [18,19].…”

Section: Introductionmentioning

confidence: 99%