A Monte Carlo method has been developed for the calculation of binary diffusion coefficients in gas mixtures. The method is based on the stochastic solution of the linear Boltzmann equation obtained for the transport of one component in a thermal bath of the second one. Anisotropic scattering is included by calculating the classical deflection angle in binary collisions under isotropic potential. Model results are compared to accurate solutions of the Chapman-Enskog equation in the first and higher orders. We have selected two different cases, H(2) in H(2) and O in O(2), assuming rigid spheres or using a model phenomenological potential. Diffusion coefficients, calculated in the proposed approach, are found in close agreement with Chapman-Enskog results in all the cases considered, the deviations being reduced using higher order approximations. (C) 2011 Elsevier Inc. All rights reserved.

The physics of vibrational kinetics in nitrogen-containing plasma produced by collisions with elec- trons is studied on the basis of recently derived cross sections and rate coefficients for the reso- nant vibrational-excitation by electron-impact. The temporal relaxation of the vibrational energy and of the vibrational distribution function is analyzed in a state-to-state approach. The electron and vibrational temperatures are varied in the range [0-50000] K. Conclusions are drawn with respect to the derivation of reduced models and to the accuracy of a relaxation time formalism. An analytical fit of the vibrational relaxation time is given.

The deconvolution of temperature dependent rate coefficients to energy dependent cross sections is accomplished by using a nonlinear optimization technique. The suggested method is successfully applied to atom-molecule and molecule-molecule dissociation processes in hydrogen.

The space exploration is nowadays assisted by realistic modeling of re-entry conditions of space vehicles in planetary atmospheres, for the design of thermal protection systems. The detailed kinetic modeling relies on the accurate description of elementary process dynamics, including the role of the excitation of the internal degrees of freedom of chemical species. Efforts in the construction of a complete and consistent dynamical information are presented, focusing on hydrogen plasmas relevant to the Jupiter atmosphere. Examples of numerical experiments are given, emphasizing the relevance of the adopted state-to-state approach in reproducing the onset of non-equilibrium internal distributions governing the plasma system evolution. © Springer-Verlag 2011.

The space exploration is nowadays assisted by realisticmodeling of re-entry conditions of space vehicles inplanetary atmospheres, for design of thermal protection systems.The detailed kinetic modeling relies on the accuratedescription of elementary process dynamics, including therole of the excitation of the internal degrees of freedom ofchemical species. Efforts in the construction of a completeand consistent dynamical information are presented, focusingon hydrogen plasmas relevant to the Jupiter atmosphere.Examples of numerical experiments are given, emphasizingthe relevance of the adopted state-to-state approach inreproducing the onset of non-equilibrium internal distributionsgoverning the plasma-system evolution.

Kinetic modelling of nonequilibrium flows is described as it applies to hypersonic phenomenology. A Monte Carlo method is described for the study of species separation on shock wave fronts; a Particle in Cell with Monte Carlo Collisions (PIC/MCC) technique is described for the simulation of dust in plasma flows; modelling of nonequilibrium radiation in shock heated gases; implementation of slip models for the description of separation zones occurring in shock- boudary layer interactions.

We investigate a kinetic model for H-H-2 mixtures in a regime where translational/rotational and vibrational-resonant energy exchanges are fast whereas vibrational energy variations are slow. In a relaxation regime, the effective volume viscosity is found to involve contributions from the rotational volume viscosity, the vibrational volume viscosity, the relaxation pressure, and the perturbed source term. In the thermodynamic equilibrium limit, the sum of these four terms converges toward the one-temperature two-mode volume viscosity. The theoretical results are applied to the calculation of the volume viscosities of molecular hydrogen in the trace limit on the basis of a complete set of state-selected cross sections for the H + H-2(v, j) system.

Acoustical shock waves (Mach number < 2) generated in situ by spark gap are propagated in weakly ionized dc discharges working at low pressure (399 Pa) and containing either Ar or N2 gas. The electrical characterization and the laser deflection technique are used to measure the characteristics of dc discharge (such as voltage, resistance and power of discharge) and the structure and velocity of shock wave, respectively. The results stress the importance of atomic and molecular nature of the gases in affecting the power deposition and the shock wave properties.

Transport properties of high-temperature helium and hydrogen plasmas as well as Jupiter atmosphere have been calculated for equilibrium and nonequilibrium conditions using higher approximations of the Chapman-Enskog method. A complete database of transport cross sections for relevant interactions has been derived, including minority species, by using both ab initio and phenomenological potentials Inelastic collision integrals terms, due to resonant charge-exchange channels, have been also considered.