Validation of Multitemperature Nozzle Flow Code
01 Jan 1995-Journal of Thermophysics and Heat Transfer (American Institute of Aeronautics and Astronautics)-Vol. 9, Iss: 1, pp 9-16
TL;DR: In this paper, a computer code nozzle in n-temperatures (NOZNT) was proposed to calculate one-dimensional flows of partially dissociated and ionized air in an expanding nozzle.
Abstract: A computer code nozzle in n-temperatures (NOZNT), which calculates one-dimensional flows of partially dissociated and ionized air in an expanding nozzle, is tested against three existing sets of experimental data taken in arcjet wind tunnels. The code accounts for the differences among various temperatures, i.e., translational-rotational temperature, vibrational temperatures of individual molecular species, and electron-electronic temperature, and the effects of impurities. The experimental data considered are (1) the spectroscopic emission data; (2) electron beam data on vibrational temperature; and (3) mass-spectrometric species concentration data. It is shown that the impurities are inconsequential for the arcjet flows, and the NOZNT code is validated by numerically reproducing the experimental data.
Citations
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TL;DR: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed in this paper, including the nonequilibrium thermochemical relaxation phenomena behind a wave surrounding the flying object.
Abstract: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed, including the nonequilibrium thermochemical relaxation phenomena occurring behind a shock wave surrounding the flying object, problems related to aerobraking maneuver, the radiation phenomena for shock velocities of up to 12 km/sec, and the determination of rate coefficients for ionization reactions and associated electron-impact ionization reactions. Results of experiments are presented in form of graphs and tables, giving data on the reaction rate coefficients for air, the ionization distances, thermodynamic properties behind a shock wave, radiative heat flux calculations, Damkoehler numbers for the ablation-product layer, together with conclusions.
1,287 citations
01 Sep 1993
TL;DR: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed in this article, including the nonequilibrium thermochemical relaxation phenomena behind a wave surrounding the flying object.
Abstract: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed, including the nonequilibrium thermochemical relaxation phenomena occurring behind a shock wave surrounding the flying object, problems related to aerobraking maneuver, the radiation phenomena for shock velocities of up to 12 km/sec, and the determination of rate coefficients for ionization reactions and associated electron-impact ionization reactions. Results of experiments are presented in form of graphs and tables, giving data on the reaction rate coefficients for air, the ionization distances, thermodynamic properties behind a shock wave, radiative heat flux calculations, Damkoehler numbers for the ablation-product layer, together with conclusions.
149 citations
TL;DR: A review of the governing equations, boundary conditions and the associated inputs by way of physico-chemical models and their partially successful application is given in this article, where some of the "rate-limiting" steps in achieving predictive capability via CFD are related to inadequacies in the physico chemical models and in associated data used in describing the multi-species hightemperature chemically reacting gas flows occurring in and around hypersonic vehicles.
132 citations
TL;DR: In this article, four experimental methods of determining the enthalpy of the flow in an arc-jet facility that is, the heat balance method, the sonic throat method, heat transfer method, and the emission-spectroscopic method, are compared with a computational fluid dynamics (CFD) solution.
Abstract: Four experimental methods of determining the enthalpy of the flow in an arc-jet facility that is, the heat balance method, the sonic throat method, the heat transfer method, and the emission-spectroscopic method, are compared with a computational fluid dynamics (CFD) solution. The comparison is made for the Interaction Heating Facility of NASA Ames Research Center for one operating condition. The mass-averaged enthalpy values determined by the heat-balance method and the sonic throat method are 28.7 and 28.8 MJ/kg, respectively. The lower bound of the centerline enthalpy value determined by the heat transfer rate method is 30.5 MJ/kg. The spectrometric method resulted in the centerline enthalpy value of 40.6 MJ/kg. The CFD solution yields the centerline and the average enthalpy values at the nozzle throat of 41.0 and 27.0 MJ/kg, respectively.
52 citations
TL;DR: In this article, an analysis model of plasma flow and electromagnetic waves around a reentry vehicle for radio frequency blackout prediction during aerodynamic heating was developed, which was validated based on experimental results from the radio attenuation measurement program.
Abstract: An analysis model of plasma flow and electromagnetic waves around a reentry vehicle for radio frequency blackout prediction during aerodynamic heating was developed in this study. The model was validated based on experimental results from the radio attenuation measurement program. The plasma flow properties, such as electron number density, in the shock layer and wake region were obtained using a newly developed unstructured grid solver that incorporated real gas effect models and could treat thermochemically non-equilibrium flow. To predict the electromagnetic waves in plasma, a frequency-dependent finite-difference time-domain method was used. Moreover, the complicated behaviour of electromagnetic waves in the plasma layer during atmospheric reentry was clarified at several altitudes. The prediction performance of the combined model was evaluated with profiles and peak values of the electron number density in the plasma layer. In addition, to validate the models, the signal losses measured during communication with the reentry vehicle were directly compared with the predicted results. Based on the study, it was suggested that the present analysis model accurately predicts the radio frequency blackout and plasma attenuation of electromagnetic waves in plasma in communication.
39 citations
Additional excerpts
...(34) The relaxation time ⟨τs⟩e−V is obtained using Lee’s work [32]....
[...]
...Because the translationalelectron energy couplings for O2 and NO are slower than that for N2, the relaxation times for O2 and NO are obtained by multiplying that for N2 by 300, as proposed by Park and Lee [33]....
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References
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TL;DR: In this article, a large number of data points for the vibrational relaxation time (pτv in atm sec) of simple systems have been logarithmically plotted vs (T°K)-⅓.
Abstract: A large number of data points for the vibrational relaxation time (pτv in atm sec) of simple systems have been logarithmically plotted vs (T°K)—⅓. It appears that each system is well represented by a straight line, and that most of these straight lines when extended to higher temperatures intersect near the point [pτv=10—8 atm sec, (T°K)—⅓=0.03]. Systems with a small reduced mass μ are exceptions to such a simple convergence, and in an improved scheme, the location of the convergence point is dependent on the reduced mass. Such a presentation has lead to an empirical equation correlating available measurements of vibrational relaxation times: log10(pτv)=(5.0×10−4)μ12θ43[T−13−0.015μ14]−8.00, where θ is the characteristic temperature of the oscillator in K deg. This equation reproduces the measured times within 50% for systems as diverse as N2, I2, and O2–H2. In the worst case thus far, O2–Ar near 1000°K, it is off by a factor of 5.
1,678 citations
Book•
01 Jan 1989TL;DR: In this paper, nonequilibrium phenomena in hypersonic flows are examined on the basis of theoretical models and selected experimental data, in an introduction intended for second-year graduate students of aerospace engineering.
Abstract: Nonequilibrium phenomena in hypersonic flows are examined on the basis of theoretical models and selected experimental data, in an introduction intended for second-year graduate students of aerospace engineering. Chapters are devoted to the physical nature of gas atoms and molecules, transitions of internal states, the formulation of the master equation of aerothermodynamics, the conservation equations, chemical reactions in CFD, the behavior of air flows in nonequilibrium, experimental aspects of nonequilibrium flow, a review of experimental results, and gas-solid interaction. Diagrams, graphs, and tables of numerical data are provided.
1,331 citations
TL;DR: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed in this paper, including the nonequilibrium thermochemical relaxation phenomena behind a wave surrounding the flying object.
Abstract: A number of chemical-kinetic problems related to phenomena occurring behind a shock wave surrounding an object flying in the earth atmosphere are discussed, including the nonequilibrium thermochemical relaxation phenomena occurring behind a shock wave surrounding the flying object, problems related to aerobraking maneuver, the radiation phenomena for shock velocities of up to 12 km/sec, and the determination of rate coefficients for ionization reactions and associated electron-impact ionization reactions. Results of experiments are presented in form of graphs and tables, giving data on the reaction rate coefficients for air, the ionization distances, thermodynamic properties behind a shock wave, radiative heat flux calculations, Damkoehler numbers for the ablation-product layer, together with conclusions.
1,287 citations
TL;DR: In this paper, an analytic expression is given for the distribution maintained by the vibration-vibration mechanism of a simple harmonic oscillator, which reduces to the usual Boltzmann-like distribution defined by a single vibrational temperature.
Abstract: The terms in the master equation for vibrational relaxation of anharmonic oscillators are ordered according to the rates of the relaxation processes (vibrational exchange, vibrational‐energy transfer to translation). The population distributions in the master equation are expanded about their values when the vibration‐vibration mechanism is the only one present. An analytic expression is given for the distribution maintained by the vibration‐vibration mechanism. In the limiting case of the simple harmonic oscillator, this distribution reduces to the usual Boltzmann‐like distribution defined by a single vibrational temperature. The general solution also applies to a mixture of simple‐harmonic‐oscillator gases of different fundamental frequencies. For such a mixture, each gas relaxes in a Boltzmann‐like distribution, but the different gases have different (but related) vibrational temperatures at any given time. The relaxation of the first moment of the distribution function also has been investigated. Anharmonicity causes a marked departure from the Landau‐Teller model of vibrational relaxation under conditions of high vibrational energy, coupled with low translational temperature. For such conditions, the populations of the lower vibrational states can be considerably lower than those predicted by the Landau‐Teller model. Furthermore, the over‐all energy relaxation rate can be accelerated.
703 citations
01 Jan 1984
TL;DR: A detailed survey of high-temperature N/H/O reactions and rate constants can be found in this paper, including reactions for which limited or no rate data are available currently as well as reactions which have undergone critical reviews previously or in this study.
Abstract: Current interest in high-temperature N/H/O kinetics stems primarily from the practical importance of combustion-generated emissions of nitrogen oxides (NOx). The recognition of air pollution as a problem of societal concern has prompted a concentrated research effort on the kinetics of NOx formation and decomposition and has led to a considerable expansion in the fundamental data base for rate constants of elementary reactions in the N/H/O system. The objectives of this survey are twofold: (1) to provide critical rate constant evaluations of reactions for which high-temperature data have been recently acquired, with due consideration given to previous evaluations, particularly the widely used survey at Leeds University (Baulch, et al., 1973); and (2) to provide an extensive compilation of N/H/O reactions and rate constants including both nonevaluated and evaluated reactions, that is, reactions for which limited or no rate data are available currently as well as reactions which have undergone critical reviews previously or in this study.
282 citations