Development of a nonequilibrium radiative heating prediction method for coupled flowfield solutions

Hartung, Lin C.

doi:10.2514/3.11542

Cited by 48 publications

(8 citation statements)

References 9 publications

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“…The agreement with the data for these nonequilibrium cases was not very good, but since they did not present values for the integrated intensity between 2.2 and 4.1 eV, it is difficult to quantify the disagreement. From Figure 5 of Hartung 20 and Figures 6 and 7 presented by Greendyke 21 , it is suspected that the non-Boltzmann modeling of N 2 and N 2 + are likely responsible for this poor agreement with the data. The 2.2 to 4.1 eV region of the spectrum is dominated by the N 2 (1 + ) and N 2 + (1 -) bands, which emit strongly in the nonequilibrium region near the shock.…”

Section: Review Of Past Studiesmentioning

confidence: 90%

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

Johnston

Hollis

Sutton

2008

Journal of Spacecraft and Rockets

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This paper presents a detailed analysis of the shock-layer radiative heating to the Fire II vehicle using a new air radiation model and a viscous shock-layer flowfield model. This new air radiation model contains the most up-to-date properties for modeling the atomic-line, atomic photoionization, molecular band, and non-Boltzmann processes. The applied viscous shock-layer flowfield analysis contains the same thermophysical properties and nonequilibrium models as the LAURA Navier-Stokes code. Radiation-flowfield coupling, or radiation cooling, is accounted for in detail in this study. It is shown to reduce the radiative heating by about 30% for the peak radiative heating points, while reducing the convective heating only slightly. A detailed review of past Fire II radiative heating studies is presented. It is observed that the scatter in the radiation predicted by these past studies is mostly a result of the different flowfield chemistry models and the treatment of the electronic state populations. The present predictions provide, on average throughout the trajectory, a better comparison with Fire II flight data than any previous study. The magnitude of the vacuum ultraviolet (VUV) contribution to the radiative flux is estimated from the calorimeter measurements. This is achieved using the radiometer measurements and the predicted convective heating. The VUV radiation predicted by the present model agrees well with the VUV contribution inferred from the Fire II calorimeter measurement, although only when radiation-flowfield coupling is accounted for. This agreement provides evidence that the present model accurately models the VUV radiation, which is shown to contribute significantly to the Fire II radiative heating. ν / c VUV = vacuum ultraviolet; refers to the spectral region above 6 eV Nomenclature

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Section: Review Of Past Studiesmentioning

confidence: 90%

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

Johnston

Hollis

Sutton

2008

Journal of Spacecraft and Rockets

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“…Modeling the radiative sources in hypersonic shock layers and fluxes to a spacecraft is a complex task and we mention here only some of the important work in this field. The Langley LORAN code [2] and the NEQAIR code [3] have been used extensively in many atmospheric entry radiative simulations. NEQAIR includes atomic bound-bound, bound-free, free-free transition, and line-by-line models for molecular bands.…”

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confidence: 99%

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

Sohn

Bansal

Levin

et al. 2010

Journal of Thermophysics and Heat Transfer

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Efficient schemes for databasing emission and absorption coefficients are developed to model radiation from hypersonic nonequilibrium flows. For bound-bound transitions, spectral information including the line-center wavelength and emission and absorption coefficients is stored for typical air plasma species. Since the flow is nonequilibrium, a rate equation approach including both collisional and radiatively induced transitions is used to calculate the electronic state populations, assuming quasi steady state. The general Voigt line-shape function is assumed for modeling the line-broadening. The accuracy and efficiency of the databasing scheme was examined by comparing results of the databasing scheme with those of NEQAIR for the Stardust flowfield. An accuracy of approximately 1% was achieved with an efficiency about three times faster than the NEQAIR code. Nomenclature A = Einstein coefficient for spontaneous emission, s 1 Ac; i = Einstein coefficient for spontaneous emission from continuum state to state i, cm 3 s 1 Ai; c = Einstein coefficient for photoionization from state i to continuum state, s 1 Ai; j = Einstein coefficient for spontaneous emission from state i to state j, s 1 a 0 = Bohr radius, 5:29167 10 9 cm B = Einstein coefficient for stimulated emission and absorption, cm 3 -m=J-s B V U = rotational constant, cm 1 b = exponent C, D = vector assembled by excitation rate coefficients of atom C m , D m = vector assembled by excitation and dissociation rate coefficients of molecule c = speed of light, 2:9979 10 10 cm s 1 D w = Doppler line half-width, cm d = parameter in the Voigt width [Eq. (34)] d ff = correction factor for free-free radiation E i = electronic term energy for atomic level i, cm 1 E k = kinetic energy of free electron, cm 1 E emis = total emission energy, W=cm 3 E 1 = ionization energy of an atom, cm 1 e = electron charge, 4:8030 10 10 statC F = rotational term energy for a molecule, cm 1 F i = assembled collisional and radiative coefficient of electronic state i G = vibrational term energy for a molecule, cm 1 GF = Gaunt factor for bound-free radiation G i = assembled collisional and radiative coefficient of electronic state i g = degeneracy H = data points of electron number density and electron temperature h = Planck's constant, 6:6262 10 34 Js J = rotational quantum number j = data point index Kc; i = recombination rate coefficient of collisional transition from continuum state to state i, cm 6 s 1 Ki; c = excitation rate coefficient of collisional transition from state i to continuum state, cm 3 s 1 K Wi = heavy-particle-induced recombination rate coefficient, cm 3 s 1 K W i; j = heavy-particle-induced molecular excitation rate coefficient from state i to state j, cm 3 s 1 K e i; j = excitation rate coefficient of collisional transition from state i to state j by electron impact, cm 3 s 1 K e ci = electron-induced recombination rate coefficient, cm 3 s 1 k = Boltzmann's constant, 1:3806 10 23 JK 1 l = number of electronic states for bound-free transition l m = number of electroni...

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“…A smeared rotational band (SRB) approach is applied for modeling the molecular band systems 33 . Of interest in the present study are the N 2 + (1-), N 2 (2+), and CN violet band systems, which contribute to the 290 -480 nm spectral range considered in Section VI.…”

Section: Radiation Modelingmentioning

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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Development of a nonequilibrium radiative heating prediction method for coupled flowfield solutions

Cited by 48 publications

References 9 publications

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

Advanced Radiation Calculations of Hypersonic Reentry Flows Using Efficient Databasing Schemes

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

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