burns_2018#
R. A. Burns, C. J. Peters and P. M. Danehy, “Unseeded velocimetry in nitrogen for high-pressure, cryogenic wind tunnels: part I. Femtosecond-laser tagging”, Meas. Sci. Technol. 29, 115302 (2018)
Source record · Catalogue · Review register
Source kind: measurement
Recorded technique: Femtosecond laser electronic excitation tagging (FLEET) velocimetry in the NASA Langley 0.3 m Transonic Cryogenic Tunnel (nitrogen): a regeneratively amplified Ti:sapphire laser (800 nm, 20 nm bandwidth, 1 kHz, about 1.2 mJ of which about half reaches the flow) focused by an f = 200 mm lens; the N2 first-positive emission of the tagged spot imaged by an intensified high-speed camera; 89-275 K, 85-400 kPa, Mach 0.2-0.75 (PDF pp. 3-6).
Materials in structured entries: None recorded.
Dataset quantities: None recorded.
Contents: 0 datasets; 0 formulas.
Curation notes#
Context only, no datasets. Identity checked on the article’s first page (PDF page 2; PDF page 1 is a cover sheet): Burns, Peters and Danehy, Meas. Sci. Technol. 29, 115302 (2018); page numbers are the PDF’s. The pulse duration is not stated.
What it shows: the FLEET signal (nitrogen emission that follows the femtosecond pulse, from N-atom recombination and excited N2) scales linearly with the gas density, and its lifetimes fall with density, ‘with little independent sensitivity to the other thermodynamic conditions’ (abstract). Table 1 (PDF p. 9) fits the two lifetimes of a tri-exponential decay as tau / tau_ref = C1 (rho / rho_ref + C2)^C3 (Eq. 2): tau_1, tau_ref = 21.6 us, rho_ref = 1.15 kg m^-3, C1 = 2.42, C2 = 0.395, C3 = -1.57; tau_2, 69.1 us, 1.15, 1.30, 0.013, -1.27; ‘purely empirical in nature’ (PDF p. 9).
Why nothing is taken: the lifetimes describe the decay of the tagged spot’s emission in a flowing, laser-heated gas, not a property of a molecule (not a dissociation time or a rate coefficient), and the authors give no physical attribution to the fit (PDF p. 9). The kinetics behind the signal are modelled in peters_2019 (C. J. Peters is an author of both). The velocity accuracy and precision results are outside optmat’s scope.
Register: TC-981.
Recorded bibliographic identity status: VALIDATED. This concerns identification of the source; it does not establish the scientific correctness of its contents.
Datasets#
No datasets are recorded.
Formulas#
No formulas are recorded.
Corrections#
No dataset errata are recorded in this source record.
Formula corrections, where recorded, appear with their formulas above. Curation notes may also discuss corrections or unresolved interpretation. Consult the review register for the checks and decisions.