General Introduction

Abstract

The production of high temperatures in gases constitutes one major feature of shock waves which represent one of the best means to transform kinetic energy into thermal energy. One of the most important consequences lies in the physical and chemical phenomena which may arise from these high temperatures such as rotational and vibrational excitation of molecules, dissociation, ionization and various chemical reactions, as well as associated radiation. Another fundamental feature proceeds from the fact that, in collisional regime (continuum), the shock wave may be considered as a discontinuity, so that the temperature rise is quasi-instantaneous. Thus, as the characteristic time required for the development of the physical and chemical phenomena is non-negligible, since it is related to collisions between elementary particles, the gaseous medium behind shock waves is in a non-equilibrium thermodynamic and chemical state.