Foreword. Part 1: Semi-Empirical Modeling of Turbulent Multicomponent Gases. 1. Turbulence in Natural Media. 2. Regular Motion of Gaseous Mixtures Involving Physicochemical Interactions of the Components. 3. Turbulent Motion of Multicomponent Mixtures with Variable Thermophysical Properties. 4. Evolutionary Transfer Models for the Second Correlation Moments. 5. The Stefan-Maxwell Relations and the Heat Flux for Turbulent Multicomponent Continuum Media. Part II: Some Model Problems of Multicomponent Turbulence. 6. Diffusion Processes in the Thermosphere. 7. Turbulent Transfer Coefficients in Planetary Upper Atmospheres: A Semi-Empirical Determination. 8. Statistical Parameters of Turbulence: Modeling from Fluctuations of the Refractive Index. 9. The Processes of Heat and Mass Transfer and Coagulation in Protoplanetary Gas-Dust Nebula. Conclusion. References. Subject Index.

Space exploration and advanced astronomy have dramatically expanded our knowledge of outer space and made it possible to study the indepth mechanisms underlying various natural phenomena caused by complex interaction of physical-chemical and dynamical processes in the universe. Huge breakthroughs in astrophysics and the planetary s- ences have led to increasingly complicated models of such media as giant molecular clouds giving birth to stars, protoplanetary accretion disks associated with the solar system's formation, planetary atmospheres and circumplanetary space. The creation of these models was promoted by the development of basic approaches in modern - chanics and physics paralleled by the great advancement in the computer sciences. As a result, numerous multidimensional non-stationary problems involving the analysis of evolutionary processes can be investigated using wide-range numerical experiments. Turbulence belongs to the most widespread and, at the same time, the most complicated natural phenomena, related to the origin and development of organized structures (- dies of different scale) at a definite flow regime of fluids in essentially non-linear - drodynamic systems. This is also one of the most complex and intriguing sections of the mechanics of fluids. The direct numerical modeling of turbulent flows encounters large mathematical difficulties, while the development of a general turbulence theory is hardly possible because of the complexity of interacting coherent structures. Three-dimensional non-steady motions arise in such a system under loss of la- nar flow stability defined by the critical value of the Reynolds number.