Radiative transfer in LTE air plasmas for temperatures up to

Chauveau, Sophie; Deron, Christine; Perrin, Marie‐Yvonne; Rivière, Philippe; Soufiani, Anouar

doi:10.1016/s0022-4073(02)00080-8

Cited by 71 publications

(38 citation statements)

References 37 publications

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“…Briefly, it is based on a set of atomic levels and lines obtained from the National Institute of Standards and Technology (NIST) online database 48 and the Opacity Project 49 , as well as atomic bound-free cross sections from the TOPbase 50 . The negative nitrogen and oxygen ions are treated using cross sections suggested by Soon and Kunc 51 and Chauveau et al 52 , respectively. The molecular band systems are treated using a smeared-rotational band (SRB) model 53 , which was shown by Johnston et al 46 to be sufficient for treating VUV absorbing and optically-thin emitting band systems in air.…”

Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2009

Journal of Spacecraft and Rockets

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Using the coupled ablation and radiation capability recently included in the LAURA flowfield solver, this paper investigates the influence of ablation on the shock-layer radiative heating for Earth entry. The extension of the HARA radiation model, which provides the radiation predictions in LAURA, to treat a gas consisting of the elements C, H, O, and N is discussed. It is shown that the absorption coefficient of air is increased with the introduction of the C and H elements. A simplified shock layer model is studied to show the impact of temperature, as well as the abundance of C and H, on the net absorption or emission from an ablation contaminated boundary layer. It is found that the ablation species reduce the radiative flux in the vacuum ultraviolet, through increased absorption, for all temperatures. However, in the infrared region of the spectrum, the ablation species increase the radiative flux, through strong emission, for temperatures above 3,000 K. Thus, depending on the temperature and abundance of ablation species, the contaminated boundary layer may either provide a net increase or decrease in the radiative flux reaching the wall. To assess the validity of the coupled ablation and radiation LAURA analysis, a previously analyzed Mars-return case (15.24 km/s), which contains significant ablation and radiation coupling, is studied. Exceptional agreement with previous viscous shock-layer results is obtained. A 40% decrease in the radiative flux is predicted for ablation rates equal to 20% of the free-stream mass flux. The Apollo 4 peak-heating case (10.24 km/s) is also studied. For ablation rates up to 3.4% of the free-stream mass flux, the radiative heating is reduced by up to 19%, while the convective heating is reduced by up to 87%. Good agreement with the Apollo 4 radiometer data is obtained by considering absorption in the radiometer cavity. For both the Mars return and the Apollo 4 cases, coupled radiation alone is found to reduce the radiative heating by 30 -60% and the convective heating by less than 5%. = thickness of the constant-property layers defined in Fig. 3, with i = 1 or 2 (cm) h = absorption coefficient (cm -1 ) = blowing reduction parameter = trasmissivity defined in Eq. (2) Subscripts h = indicates a spectral dependence in terms of eV Superscripts abl = refers to ablation species, meaning species containing any C or H atoms air = refers to air species, meaning species containing no C or H atoms Abbreviations eV = electron volts; the frequency in eV, labeled h , is equal to 1.24x10 -4 / c IR = infrared; refers here to the spectral region below 6 eV NIST = National Institute of Standards and Technology OP = Opacity Project VUV = vacuum ultraviolet; refers to the spectral region above 6 eV

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Section: Radiation Modeling Of Air With Ablation Productsmentioning

confidence: 99%

Influence of Ablation on Radiative Heating for Earth Entry

Johnston

Gnoffo

Sutton

2009

Journal of Spacecraft and Rockets

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“…This subtracted component is interpreted as being a result of measurement calibration or flowfield contamination. It could also be interpreted as coming from a radiation mechanism in N or O that is not treated in the present model, such as the negative continuum 39 . This possibility requires further study.…”

Section: Molecular Band Emission In the 290 -480 Nm Wavelength Rangementioning

confidence: 99%

A Comparison of EAST Shock-Tube Radiation Measurements with a New Air Radiation Model

Johnston

2008

46th AIAA Aerospace Sciences Meeting and Exhibit

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This paper presents a comparison between the recent EAST shock tube radiation measurements (Grinstead et al., AIAA 2008-1244) and the HARA radiation model. The equilibrium and nonequilibrium radiation measurements are studied for conditions relevant to lunar-return shock-layers; specifically shock velocities ranging from 9 to 11 km/s at initial pressures of 0.1 and 0.3 Torr. The simulated shock-tube flow is assumed one-dimensional and is calculated using the LAURA code, while a detailed nonequilibrium radiation prediction is obtained in an uncoupled manner from the HARA code. The measured and predicted intensities are separated into several spectral ranges to isolate significant spectral features, mainly strong atomic line multiplets. The equations and physical data required for the prediction of these strong atomic lines are reviewed and their uncertainties identified. The 700 -1020 nm wavelength range, which accounts for roughly 30% of the radiative flux to a peak-heating lunar return shock-layer, is studied in detail and the measurements and predictions are shown to agree within 15% in equilibrium. The ±1.5% uncertainty on the measured shock velocity is shown to cause up to a ±30% difference in the predicted radiation. This band of predictions contains the measured values in almost all cases. For the highly nonequilibrium 0.1 Torr cases, the nonequilibrium radiation peaks are under-predicted by about half. This under-prediction is considered acceptable when compared to the order-of-magnitude over-prediction obtained using a Boltzmann population of electronic states. The reasonable comparison in the nonequilibrium regions provides validation for both the non-Boltzmann modeling in HARA and the thermochemical nonequilibrium modeling in LAURA. The N 2 + (1-) and N 2 (2+) molecular band systems are studied in the 290 -480 nm wavelength range for both equilibrium and nonequilibrium regimes. The nonBoltzmann rate models for these systems, which have significant uncertainties, are tuned to improve the comparison with measurements. Nomenclature B= Blackbody or Planck function written in terms of wavelength (erg/cm 3 /s/sr) c = velocity of light, equal to 2.997925x10 10 cm/s e = electron charge, equal to 4.80298x10 -10 cm 3/2 g 1/2 /s f ij = oscillator strength for the atomic line transition with a lower level i and an upper level j g i = degeneracy for an atomic level i h = Planck's constant, equal to 6.6256x10 -27 erg-s I = wavelength dependent intensity (erg/cm 3 /sr/s) j line = wavelength-integrated emission coefficient over a single atomic line or multiplet (erg/cm 3 /sr/s) j = wavelength dependent emission coefficient (erg/cm 4 /sr/s) J c = wavelength-integrated normalized intensity for a given wavelength range (erg/cm 3 /sr/s), which is often presented in this paper multiplied by 100, as indicated by *100 J line = wavelength-integrated normalized intensity for a single atomic line or multiplet (erg/cm 3 /sr/s) J other = normalized intensity resulting from atomic continuum, molecular bands, and weak atomic lines ...

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“…56,57 When data are not available for a molecular species, its radiation is neglected. More details on this complex calculation can be found in the works of the EM2C laboratory 58,59 and Laplace Laboratory. 48 method (with the Mean absorption Coefficients defined according to different mean functions) are used in this paper.…”

Section: Estimation Of the Radiative Lossesmentioning

confidence: 99%

Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

Cressault

2015

AIP Advances

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This paper has for objectives to present the radiative and the transport properties for people beginning in thermal plasmas. The first section will briefly recall the equations defined in numerical models applied to thermal plasmas; the second section will particularly deal with the estimation of radiative losses; the third part will quickly present the thermodynamics properties; and the last part will concern the transport coefficients (thermal conductivity, viscosity and electrical conductivity of the gas or mixtures of gases). We shall conclude the paper with a discussion about the validity of these results the lack of data for some specific applications, and some perspectives concerning these properties for non-equilibrium thermal plasmas. C 2015 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. [http://dx

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Radiative transfer in LTE air plasmas for temperatures up to

Cited by 71 publications

References 37 publications

Influence of Ablation on Radiative Heating for Earth Entry

Influence of Ablation on Radiative Heating for Earth Entry

A Comparison of EAST Shock-Tube Radiation Measurements with a New Air Radiation Model

Basic knowledge on radiative and transport properties to begin in thermal plasmas modelling

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