Transport Coefficients for High-Temperature Nonequilibrium Air Flows

Numerical simulations of the plasma flow and electromagnetic wave around a membraneaeroshell type reentry vehicle were performed using various physical model combinations, and the possibility of radio frequency blackout of transceiver antenna embedded at the rear of the vehicle was investigated. The flow field was assumed to be in thermochemical nonequilibrium, and it was described by the Navier-Stokes equations with a multitemperature model and the equation of state. The simulations were performed for several altitudes including the highest heat flux point according to reentry orbit data. Through these computations, the detailed distributions of the flow-field properties in the shock layer and wake region were successfully obtained. To evaluate possibility of the radio frequency blackout during atmospheric reentry, the distribution of the electron number density around the inflatable vehicle was clarified. A frequency-dependent finite-difference time-domain method was used for simulations of electromagnetic waves, and the physical properties were obtained from the computational results of the plasma flow calculation. Electromagnetic wave behaviors in an ionized gas region behind the inflatable vehicle were investigated. It was found that the number density of electrons was sufficiently small and that the electromagnetic waves can propagate with less reflection and no attenuation. These results suggest that radio frequency blackout may not occur during the atmospheric reentry of the inflatable vehicle.

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“…However, if the medium in which the electromagnetic wave propagates is sufficiently conductive, strong [28] T-V(100 %), R-V(0 %) [11,12] …”

Section: Electron Densitymentioning

confidence: 99%

Examination of Radio Frequency Blackout for an Inflatable Vehicle During Atmospheric Reentry

Takahashi

Yamada

Abe

2014

Journal of Spacecraft and Rockets

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“…To determine the first-order transport properties, the collision cross-sections between two chemical species are required. In this study, the collision cross-sections are obtained from Gupta's work [18], except for the e-N and e-O pairs, which are calculated using the Fertig model [19,20]. The ambipolar diffusion is expressed as follows:…”

Section: Transport Propertiesmentioning

confidence: 99%

Advanced validation of CFD-FDTD combined method using highly applicable solver for reentry blackout prediction

Takahashi¹

2015

J. Phys. D: Appl. Phys.

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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.

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“…The collision cross sections are obtained using Gupta's method [20]. However, for e-N and e-O pairs, collision cross section models by Fertig et al [21,22] are used. The diffusion coefficients are expressed using the formula developed by Curtiss and Hirschfelder [23] [24].…”

Section: Governing Equationsmentioning

confidence: 99%

Advanced Validation of Nonequilibrium Plasma Flow Simulation for Arc-Heated Wind Tunnels

Takahashi

Abe

Takayanagi

et al. 2014

Journal of Thermophysics and Heat Transfer

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Turbulent plasma flows in arc heaters such as JAXA 750 kW, NASA 20 MW, and Kyushu University 20 kW facilities were investigated, and the distributions of the flowfield properties were successfully obtained. The arc discharge in the constrictor section and the expansion processes in the nozzle section play key roles in the formation of an arc-heated flow. Hence, for accurately predicting high-enthalpy flow properties, it is important to model correctly the complex phenomena observed in various-scale facilities. For this purpose, an integrated analysis model to simulate various-scale arc-heated flows with high accuracy was developed. The turbulent flow field was described using the Reynolds-averaged Navier-Stokes equations with a multitemperature model, which was tightly coupled with electric-field and radiation-field calculations. A sophisticated and low-cost radiation model and a low-Reynolds number two-equation turbulence model were introduced into the flow-field simulation. To validate the present integrated analysis model, the computed results were compared with the corresponding experimental data for the mass-averaged enthalpy, translational and rotational temperatures, and number density of nitrogen obtained through spectroscopic and laser-induced fluorescence techniques. Moreover, the mechanisms of energy input by discharge and energy loss are discussed with the distributions of the electronic excitation temperature and heat flux on the constrictor wall derived from the arc column. Although the results indicate that a relatively detailed discharge model is required to describe the arc discharge with relatively high accuracy, the present flow-field model was generally in good agreement with various operating conditions of the facilities.

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Transport Coefficients for High-Temperature Nonequilibrium Air Flows

Cited by 71 publications

References 12 publications

Examination of Radio Frequency Blackout for an Inflatable Vehicle During Atmospheric Reentry

Examination of Radio Frequency Blackout for an Inflatable Vehicle During Atmospheric Reentry

Advanced validation of CFD-FDTD combined method using highly applicable solver for reentry blackout prediction

Advanced Validation of Nonequilibrium Plasma Flow Simulation for Arc-Heated Wind Tunnels

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