Nonequilibrium Phenomena Behind Strong Shock Waves Generated in Superorbital Reentry Flight

Matsuda, Atsushi; Fujita, Kazuhisa; Sato, Shunichi; Abe, Takashi

doi:10.2514/1.6244

Cited by 20 publications

(12 citation statements)

References 4 publications

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“…Shock-tube measurements of the intensity profile behind a moving shock provide the desired spatially dependent radiation measurement. These have been reported by Allen et al 14 , Sharma 15,16,17 , Donohue et al 18 , Koreeda et al 19 , Morioka et al 20 , Fujita et al 21 , and Matsuda et al 22 . With the exception of Allen et al, these studies do not provide spectrally resolved data in the important 700 -1200 nm range.…”

Section: Introductionmentioning

confidence: 48%

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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Section: Introductionmentioning

confidence: 48%

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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“…The two-temperature model was validated and its accuracy was demonstrated by using experimental data at moderate shock velocities around 6 km/s. 3,4) However, some experimental results 5,6) showed disagreement with the model predictions at higher shock velocities around 12 km/s. Therefore, the thermochemical model to describe the nonequilibrium phenomena needs to be validated and improved by further experimental investigations in a higher shock speed range.…”

Section: Introductionmentioning

confidence: 82%

“…At 0.5-1.0 MPa in the reservoir and 5-100 kPa in the compression tube, the maximum attainable pressure and piston position obtained from Eqs. (5) and (6) are shown in Fig. 7.…”

Section: Compression By Free Piston and Attainable Pres-mentioning

confidence: 99%

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Development of Shock Tube for Ground Testing Reentry Aerothermodynamics

Yamada

Suzuki

Takayanagi

et al. 2011

Trans. Japan Soc. Aero. S Sci.

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A free-piston double-diaphragm shock tube with 70 Â 70 mm cross-section at test section is newly developed to investigate thermochemical nonequilibrium phenomena behind a shock wave. This paper presents the performance of the shock tube and the measurement system newly developed. Experimental investigations to clarify its characteristics are conducted for various operational parameters, such as rupture pressure of the first diaphragm and initial pressures in the low-pressure tube, the high-pressure tube, and the compression tube. Based on the characteristics experiment, a performance map of the shock tube is obtained by changing the operation parameters. The result shows that the shock tube can generate the post-shock condition corresponding to super-orbital reentry flight conditions. The newly developed measurement system enables us to obtain a spatial distribution of spectra behind a shock wave with high spatial and time resolution. A description of the measurement system and typical examples of the measured spectra are presented.

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“…The two-temperature model has been validated, and its accuracy has been demonstrated using experimental data at moderate shock velocities around 6 km/s. 3,4) However, some experimental results 5,6) show that the measured rotational temperature is in high nonequilibrium with the predicted translational temperature, suggesting a discrepancy in the model prediction at higher shock velocities around 12 km/s. In such cases, the measured rotational temperature was significantly lower than the predicted translational temperature.…”

Section: Introductionmentioning

confidence: 93%

Shock Layer Radiation Analysis using a Hypervelocity Shock Tube (HVST)

Yamada

Takayanagi

Suzuki

et al. 2012

Trans. Japan Soc. Aero. S Sci.

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Spectroscopic measurement is conducted using a free-piston double-diaphragm shock tube to investigate the nonequilibrium phenomena in the shock layer. The shock velocity and spectrum position correlated to the shock front are determined using a double-laser schlieren measurement system for precise localization. Emission spectra of N 2 (1þ), N 2 (2þ) and N 2 þ (1À) band systems are obtained by means of time-frozen imaging spectroscopy. A spectrum fitting method is used to determine the rotational and vibrational temperatures from the measured spectra, and temperature distribution correlated to the shock front is finally obtained. The measured rotational temperatures are in high nonequilibrium with the translational temperature expected from the numerical prediction of the two-temperature model. The measured rotational temperature for N 2 (2þ) is lower than those for N 2 (1þ) and N 2 þ (1À) immediately behind a shock wave. Hence, rotational relaxation for the N 2 C state looks slower than those for the N 2 B and N 2 þ B states. On the contrary, the measured vibrational temperatures for N 2 (1þ), N 2 (2þ) and N 2 þ (1À) are close to each other, and agree well with the numerical prediction of the two-temperature model. The experiment and numerical analysis suggest that the electronic excitation temperature is in nonequilibrium with the vibrational temperature.Key Words: Shock Tube, Re-entry, Nonequilibrium, Shock Wave, Emission Spectroscopy Nomenclature L: spectrum position from the shock front, mm n: number density, particles/m 3 P 0 : ambient pressure ahead of shock wave, Pa T t : translational temperature, K T r : rotational temperature, K T v : vibrational temperature, K T ex : electronic excitation temperature, K V: shock velocity, km/s

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Nonequilibrium Phenomena Behind Strong Shock Waves Generated in Superorbital Reentry Flight

Cited by 20 publications

References 4 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

Development of Shock Tube for Ground Testing Reentry Aerothermodynamics

Shock Layer Radiation Analysis using a Hypervelocity Shock Tube (HVST)

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