Introduction

Abstract

For the recent decades, the kinetic theory of gases has encountered a necessity to solve some new physical problems. One of them is modeling of gas flows under the conditions of strong deviations from thermodynamic equilibrium. Such conditions occur, for example, near surfaces of nonexpendable space vehicles in their reentry into the Earth atmosphere, in experiments carried out with high-enthalpy facilities, in supersonic gas flows in nozzles and jets, for various types of energy pumping into vibrational and electronic degrees of freedom.

In high-temperature and hypersonic flows of gas mixtures, the energy exchange between translational and internal degrees of freedom, chemical reactions, ionization and radiation may result in noticeable violation of thermodynamic equilibrium. In particular, it was found that a large section of descending trajectory of modern space vehicles in the course of their reentry into the Earth atmosphere lies at large heights (60 to 70 km), where the gas is substantially rarefied (its pressure there is of the order of 10^− 2 atm) and the characteristic times of kinetic and gas-dynamic processes are comparable. Therefore the non-equilibrium effects become of importance for a hypersonic flow and should be taken into account for the prediction of the flow parameters.