Study of equilibrium air total radiation

Gruszczynski, J. S.; Warren, W. R.

doi:10.2514/6.1966-103

Cited by 5 publications

(2 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Apollo 4 radiometer measurements 8 have similar limitations, as well as the added complexity of ablation products being present in the shock-layer. In addition to these two flight experiments, there have been several laboratory measurements of the radiative intensity reaching the body of a model placed in a shock tube 9,10,11,12 . These have been reviewed and compared with the RAD/EQUIL code by Sutton 13 , but they also lack the desired spatial and spectral dependence.…”

Section: Introductionmentioning

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

View full text Add to dashboard Cite

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 ...

show abstract

Section: Introductionmentioning

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

View full text Add to dashboard Cite

show abstract

“…The shock tube experiments considered are by Hoshizaki, 141 Thomas and Menard, 142 Nerem, 143 and Gruszynski and Warren. 144 These experiments all measured the spectrally-integrated radiative intensity between 0 and 6 eV at the stagnation point of a small model placed in the shock tube. With free-stream shock tube velocities and pressures up to 1.0 Torr and 10 km/s, temperatures up to 16,000 K were obtained within the shock layer of the model.…”

Section: Part II Comparison With 1960s Era Shock Tube Measurements Ximentioning

confidence: 99%

Assessment of Radiative Heating Uncertainty for Hyperbolic Earth Entry

Johnston

Mazaheri

Gnoffo

et al. 2011

42nd AIAA Thermophysics Conference

View full text Add to dashboard Cite

This paper investigates the shock-layer radiative heating uncertainty for hyperbolic Earth entry, with the main focus being a Mars return. In Part I of this work, a baseline simulation approach involving the LAURA Navier-Stokes code with coupled ablation and radiation is presented, with the HARA radiation code being used for the radiation predictions. Flight cases representative of peak-heating Mars or asteroid return are defined and the strong influence of coupled ablation and radiation on their aerothermodynamic environments are shown. Structural uncertainties inherent in the baseline simulations are identified, with turbulence modeling, precursor absorption, grid convergence, and radiation transport uncertainties combining for a +34% and −24% structural uncertainty on the radiative heating. A parametric uncertainty analysis, which assumes interval uncertainties, is presented. This analysis accounts for uncertainties in the radiation models as well as heat of formation uncertainties in the flowfield model. Discussions and references are provided to support the uncertainty range chosen for each parameter. A parametric uncertainty of +47.3% and −28.3% is computed for the stagnation-point radiative heating for the 15 km/s Mars-return case. A breakdown of the largest individual uncertainty contributors is presented, which includes C3 Swings cross-section, photoionization edge shift, and Opacity Project atomic lines. Combining the structural and parametric uncertainty components results in a total uncertainty of +81.3% and −52.3% for the Mars-return case.In Part II, the computational technique and uncertainty analysis presented in Part I are applied to 1960s era shock-tube and constricted-arc experimental cases. It is shown that experiments contain shock layer temperatures and radiative flux values relevant to the Mars-return cases of present interest. Comparisons between the predictions and measurements, accounting for the uncertainty in both, are made for a range of experiments. A measure of comparison quality is defined, which consists of the percent overlap of the predicted uncertainty bar with the corresponding measurement uncertainty bar.

show abstract

Measuring Vacuum Ultraviolet Radiation from High-Temperature Nitrogen

Compton

1967

IEEE Trans. Aerosp. Electron. Syst.

View full text Add to dashboard Cite

Study of equilibrium air total radiation

Cited by 5 publications

References 6 publications

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

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

Assessment of Radiative Heating Uncertainty for Hyperbolic Earth Entry

Measuring Vacuum Ultraviolet Radiation from High-Temperature Nitrogen

Contact Info

Product

Resources

About