Nonlinear Higher-Order Hydrodynamics. Unification of kinetic and hydrodynamic approaches within a nonequilibrium statistical ensemble formalism

Construction, in the framework of a Nonequilibrium Statistical Ensemble Formalism, of a Mesoscopic Hydro-Thermodynamics, that is, covering phenomena involving motion displaying variations short in space and fast in time -unrestricted values of Knudsen numbers-, is presented. In that way, it is provided an approach enabling for the coupling and simultaneous treatment of the kinetics and hydrodynamic levels of descriptions. It is based on a complete thermo-statistical approach in terms of the densities of matter and energy and their fluxes of all orders covering systems arbitrarily driven away from equilibrium. The set of coupled nonlinear integro-differential hydrodynamic equations is derived. They are the evolution equations of the Grad-like moments of all orders, derived from a kinetic equation built in the framework of the Nonequilibrium Statistical Ensemble Formalism. For illustration, the case of a system of particles embedded in a fluid acting as a thermal bath is fully described. The resulting enormous set of coupled evolution equations is of unmanageable proportions, thus requiring in practice to introduce an appropriate description using the smallest possible number of variables. We have obtained a hierarchy of Maxwell-times, which can be considered a kind of Bogoliubov's characteristic times in hydrodynamics and which have a particular relevance in the creteria for stablishing a contraction of description.