D. Bruno

Effect of electronic excited states on transport in magnetized hydrogen plasma

Multicomponent diffusion coefficients for magnetized, equilibrium hydrogen plasma have been calculated. The equilibrium composition of the plasma is determined by taking consistently into account the number of allowed atomic electronic excited states (EES) as determined by the average interparticle distance. The coefficients are shown to depend on the inclusion of realistic cross sections for the interactions with EES. The effect of an applied magnetic field on the diffusion coefficients and on derived quantities like the electrical conductivity and the internal and reactive thermal conductivity is studied and explained.

Direct simulation of non-equilibrium kinetics under shock conditions in nitrogen

Abstract We study the interplay of vibrational kinetics, dissociation, translational and rotational relaxation in a strong shock wave in nitrogen by Direct Simulation Monte Carlo simulation (DSMC). The input data for vibrational and chemical processes are all in the form of cross-sections, mostly determined by molecular physics methods. In particular, we use for the first time very recent Quasi-Classical Trajectory (QCT) results for cross-sections of multi-quantum VT energy exchange and dissociation in N+N 2 collisions. Non-equilibrium distributions are observed and discussed.

Transport of internal electronic energy in atomic hydrogen thermal plasmas

Reactive and internal thermal conductivities for equilibrium hydrogen plasma have been calculated by the Chapman-Enskog method. The equilibrium composition of the plasma is determined by taking consistently into account the number of allowed atomic electronic excited states (EES) as determined by the average interparticle distance. The coefficients depend on the inclusion of realistic cross sections for the interactions with EES. In particular, the interplay between the two coefficients that describe the transport of electronic and ionization energy is analyzed.

Thermodynamics, Transport and Kinetics of Equilibrium and Non-Equilibrium Plasmas: A State-to-State Approach

Thermal non-equilibrium plasmas have been deeply investigated theoretically by means of the state-to-state approach, offering the unique opportunity of a detailed information about internal distributions affecting thermodynamics, transport coefficients and kinetics, properly accounting for the presence of excited states. The efforts made in the construction of knowledge on the dynamics of elementary processes occurring in the plasma with resolution on internal degrees of freedom, required by the method, are discussed. Boltzmann equation is solved for electrons self-consistently coupled to the chemical species collisional dynamics, reproducing very interesting features of strongly non-equilibrium internal distributions, characterizing plasmas.

DSMC modelling of vibrational and chemical kinetics for a reacting gas mixture

Abstract A zero-dimensional Direct Simulation Monte Carlo (DSMC) model is developed for simulating reacting gas mixtures including state-to-state vibrational kinetics and simple bimolecular reactions. The method is applied to the simulation of three systems: translational relaxation of a hard sphere gas, vibrational relaxation of an anharmonic oscillator gas and dissociation in a simplified H 2 –Xe system. In this last case, the role of translational non-equilibrium is shown to be important in affecting the dissociation kinetics.

Cutoff criteria of electronic partition functions and transport properties of atomic hydrogen thermal plasmas

Transport coefficients of equilibrium hydrogen plasma have been calculated by using different cutoffs of electronic partition functions and different sets of transport cross sections of electronically excited states. The selection of both the cutoff criterion and transport cross sections deeply affects the transport coefficients of the H, H+, e plasma mixture in the temperature range of 10u2009000–50u2009000u2002K and in the pressure interval of 1–1000 atm.

Analytical Expressions of Thermodynamic and Transport Properties of the Martian Atmosphere in a Wide Temperature and Pressure Range

Calculation of thermodynamic and transport properties of CO2/N2/O2/Ar system (Martian atmosphere) have been performed in a wide pressure (0.01–100 bar) and temperature range (50–50,000xa0K). A self-consistent approach for the thermodynamic properties and higher order approximation of the Chapman–Enskog method for the transport coefficients have been used. Debye–Hückel corrections have been included in the calculation of thermodynamic properties while collision integrals derived following a phenomenological approach and accounting also for resonant processes contributions have been used. Moreover, charge–charge interactions have been obtained by using a screened Coulomb potential. Calculated values have been fitted by closed forms ready to be inserted in fluid dynamic codes in order to simulate plasma conditions for different technological applications. Comparison with data present in literature is also reported.

Reactive and internal contributions to the thermal conductivity of local thermodynamic equilibrium nitrogen plasma: The effect of electronically excited states

Internal and reactive contributions to the thermal conductivity of a local thermodynamic equilibrium nitrogen plasma have been calculated using the Chapman-Enskog method. Low-lying (LL) electronically excited states (i.e., states with the same principal quantum number of the ground state) and high-lying (HL) ones (i.e., states with principal quantum number n> 2) have been considered. Several models have been developed, the most accurate being a model that treats the LL states as separate species while disregarding the presence of HL states, on account of their enormous transport cross sections.

Direct simulation of non-linear interparticle collisional relaxation of ensembles of two-level systems

Abstract In this work, we study the particle kinetics of self-interacting two-level systems in gas phase. The translational relaxation is described by means of the direct simulation Monte Carlo method. The quantum state of the ensemble is described by a distribution function on the Riemann sphere as suggested in a recent paper [S. Longo, D. Bruno, M. Capitelli, P. Minelli, Chem. Phys. Lett. 316 (2000) 311]. Detailed results are presented for a uniform gas of spin 1/2 atoms relaxing under superimposed fixed and rotating magnetic fields.

A Monte Carlo model for determination of binary diffusion coefficients in gases

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, H2 in H2 and O in O2, 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.