Prediction of Nonequilibrium Air Plasma Radiation Behind a Shock Wave

Lemal, Adrien; Jacobs, Carolyn; Perrin, Marie‐Yvonne; Laux, Christophe O.; Tran, P.; Raynaud, E.

doi:10.2514/1.t4550

Cited by 43 publications

(10 citation statements)

References 36 publications

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“…This is of interest, as work by Lemal et al. (2016) reproduced this ‘dip’ feature (where other models did not) for vacuum ultraviolet atomic radiance at similar test conditions to those that are presented here. That analysis did not include deceleration effects, and only considered thermochemical modelling – specifically, various heavy-particle impact excitation models were applied.…”

Section: Shock Deceleration Effects On Test Slug Morphologysupporting

confidence: 79%

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

Collen¹,

Mare²,

Mare³

et al. 2022

J. Fluid Mech.

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Shock tubes are a crucial source of experimental data for the aerothermodynamic modelling of atmospheric entry vehicles. Notably, many chemical-kinetic and radiative models are validated directly against optical measurements from these facilities. Typically, the incident shock speed at the location of the experimental measurement is taken to be representative of the test slug; however, the shock velocity can vary substantially upstream of this location. These variations have been long posited as a source of disagreement with computational predictions, although a definitive link has proved elusive. This work describes a series of experiments which aim to isolate and confirm the importance of the shock deceleration effect. This is achieved by generating different shock trajectories and comparing the post-shock trends in atomic oxygen emission and electron density. These trends are shown to be directly linked to the upstream shock speed variations using a recently developed numerical tool (LASTA). The close agreement of the comparisons confirms the importance of shock speed variation for shock tube experiments; these findings have direct and potentially critical relevance for all such studies, both past and present.

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Section: Shock Deceleration Effects On Test Slug Morphologysupporting

confidence: 79%

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

Collen¹,

Mare²,

Mare³

et al. 2022

J. Fluid Mech.

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“…Figure shows the results of heavy-particle impact excitation rate measurements as well as theoretical predictions on an Arrhenius plot. Although a few estimates exist for electronic excitation rates due to N–N, N–O, and O–O collisions (relevant to high-temperature air CR models , ), to the authors’ knowledge, these are the first direct shock tube measurements of O* formation rates by O–Ar collisions. Best fits of the current experiments were obtained using the format k M (1, i ) = A T b exp(− C / T ), where the temperature dependence term b was fixed at 1/2 to match the dependence from the theoretical formulation, the activation energy term C was set to E i (in K), and the best fit was determined by varying the parameter A .…”

Section: Shock Tube Experimentsmentioning

confidence: 99%

“…In their study, they found that heavy-particle impact processes (N−N, N−O, O−O collisions) may play a significant role in the electronic excitation immediately after passage of the incident shock, where the gas is weakly ionized and electrons are scarce. Although this work focused particularly on the electronic excitation of atomic oxygen (a major constituent of high-temperature air) by argon at a lower-temperature regime (T < 8000 K), the weakly ionized nature of the flow suggests, analogously to Lemal et al, 24,25 that heavy-particle impact O−Ar collisions could play a dominant role in the production of O* over O−e − collisions when temperatures are "low".…”

Section: Introductionmentioning

confidence: 99%

“…Lemal et al , recently used a CR model for high-temperature air to analyze shock tube radiation measurements. Data were acquired behind fast incident shocks (∼10–11 km/s) traveling in low-pressure (∼13 Pa) air; kinetic temperatures initially behind shock waves were ∼6 × 10 4 K, quickly falling to ∼1 × 10 4 K after less than 2 μs.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of Excited Oxygen Formation in Shock-Heated O₂–Ar Mixtures

et al. 2016

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The formation of electronically excited atomic oxygen was studied behind reflected shock waves using cavity-enhanced absorption spectroscopy. Mixtures of 1% O-Ar were shock-heated to 5400-7500 K, and two distributed-feedback diode lasers near 777.2 and 844.6 nm were used to measure time-resolved populations of atomic oxygen's S° andS° electronic states, respectively. Measurements were compared with simulated population time histories obtained using two different kinetic models that accounted for thermal nonequilibrium effects: (1) a multitemperature model and (2) a reduced collisional-radiative model. The former assumed a Boltzmann distribution of electronic energy, whereas the latter allowed for non-Boltzmann populations by treating the probed electronic states as pseudospecies and accounting for dominant electronic excitation/de-excitation processes. The effects of heavy-particle collisions were investigated and found to play a major role in the kinetics of O atom electronic excitation at the conditions studied. For the first time, rate constants (k) for O atom electronic excitation from the ground state (P) due to collisions with argon atoms were directly inferred using the reduced collisional-radiative model, k(P → S°) = 7.8 × 10T exp(-1.061 × 10K/T) ± 25% cm s and k(P → S°) = 2.5 × 10T exp(-1.105 × 10K/T) ± 25% cm s.

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“…In fact, the surface temperature of a hypersonic vehicle may reach 2000 K with a non-uniform distribution [23]. The TIR emission can also be radiated from gases in the shock layer and wake flows [24]. This means that the temperature of both the aircraft's surfaces and the reacting flows may influence the evaluation of infrared optical observability.…”

Section: Introductionmentioning

confidence: 99%

Infrared Optical Observability of an Earth Entry Orbital Test Vehicle Using Ground-Based Remote Sensors

et al. 2019

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Optical design parameters for a ground-based infrared sensor rely strongly on the target’s optical radiation properties. Infrared (IR) optical observability and imaging simulations of an Earth entry vehicle were evaluated using a comprehensive numerical model. Based on a ground-based IR detection system, this model considered many physical mechanisms including thermochemical nonequilibrium reacting flow, radiative properties, optical propagation, detection range, atmospheric transmittance, and imaging processes. An orbital test vehicle (OTV) was selected as the research object for analysis of its observability using a ground-based infrared system. IR radiance contours, maximum detecting range (MDR), and thermal infrared (TIR) pixel arrangement were modeled. The results show that the distribution of IR radiance is strongly dependent on the angle of observation and the spectral band. Several special phenomena, including a strong receiving region (SRR), a characteristic attitude, a blind zone, and an equivalent zone, are all found in the varying altitude MDR distributions of mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) irradiances. In addition, the possible increase in detectivity can greatly improve the MDR at high altitudes, especially for the backward and forward views. The difference in the peak radiance of the LWIR images is within one order of magnitude, but the difference in that of the MWIR images varies greatly. Analyses and results indicate that this model can provide guidance in the design of remote ground-based detection systems.

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Prediction of Nonequilibrium Air Plasma Radiation Behind a Shock Wave

Abstract: International audienc

Cited by 43 publications

References 36 publications

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

Kinetics of Excited Oxygen Formation in Shock-Heated O₂–Ar Mixtures

Infrared Optical Observability of an Earth Entry Orbital Test Vehicle Using Ground-Based Remote Sensors

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Prediction of Nonequilibrium Air Plasma Radiation Behind a Shock Wave

Abstract: International audienc

Cited by 43 publications

References 36 publications

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

The influence of shock speed variation on radiation and thermochemistry experiments in shock tubes

Kinetics of Excited Oxygen Formation in Shock-Heated O2–Ar Mixtures

Infrared Optical Observability of an Earth Entry Orbital Test Vehicle Using Ground-Based Remote Sensors

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Kinetics of Excited Oxygen Formation in Shock-Heated O₂–Ar Mixtures