Numerical Prediction of Hypersonic Flowfields Including Effects of Electron Translational Nonequilibrium

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Numerical Prediction of Hypersonic Flowfields Including Effects of Electron Translational Nonequilibrium

Farbar, Erin / Boyd, Iain D. / Martin, Alexandre

The degree of electron thermal nonequilibrium occurring in continuum, hypersonic, slender body, and blunt body flows is investigated. The effect of thermal nonequilibrium between the electron translational and vibrational-electronic modes on the predicted electron density and electron temperature is quantified at flight conditions characteristic of a slender hypersonic vehicle, as well as at a higher energy, superorbital flight condition of a blunt reentry vehicle. The most significant effect of electron thermal nonequilibrium on the flowfield is through the influence of the electron temperature on the magnitude of the chemical reaction rates in the high density shock layer. A twofold reduction in peak plasma density is predicted in the flow around the slender body when the electron nonequilibrium model is used, and this results in better agreement between the simulation results and the experimental electron density measurements. A change in the shape of the electron density profile with the use of the electron nonequilibrium model is predicted along the stagnation streamline of the blunt body flow. In both cases, the changes in predicted electron density are much more pronounced at the higher density flight conditions examined. In all cases, the rise of the electron temperature precedes the rise of the vibrational-electronic temperature along the stagnation streamline. These results have potentially important implications for the prediction of the onset of radio frequency blackout during the flights of next generation hypersonic vehicles, a phenomenon that is governed by the properties of the electron gas.