Gianpiero Colonna

Self-Consistent Model of Chemical, Vibrational, Electron Kinetics in Nozzle Expansion

A self-consistent model to describe vibrational, electronically excited states (master equations) and free electron kinetics (Boltzmann equation) has been applied to study N 2 expansion through a converging-diverging conic nozzle. Strong departures from equilibrium can be observed for both vibrational, electronically excited states and electron energy distributions. In particular, the role of electronically excited states of nitrogen molecules and free electrons has been investigated. The strong interaction between these two systems, by means of inelastic and superelastic collisions, influences not only the internal state kinetics, but also the macroscopic quantities such as Mach number and gas temperature profile

Modelling of LIBS plasma expansion

Abstract A one-dimensional time-dependent fluid dynamic model has been developed to describe the expansion of the plume produced by laser ablation. The model includes chemical reactions considered in local thermodynamic equilibrium to describe the expansion of a TiO plasma. The results are discussed in connection with LIBS plasmas.

Reduction of State-to-State Kinetics to Macroscopic Models in Hypersonic Flows

The state-to-state chemical kinetic model, which considers a kinetic equation for each vibrational state of diatomic molecules, has been applied to some supersonic flow regimes and in particular in boundary layer, nozzle expansion, and shock wave. Nonequilibrium vibrational distribution obtained in the calculations shows strong departure from equilibrium-inducing non-Arrhenius global chemical rates, which differ substantially from macroscopic rates commonly used in fluid-dynamic codes. The evolution properties of the distribution have been investigated by a zero-dimensional numerical code in controlled conditions. We are trying to obtain from zero-dimensional results the approach to find appropriate macroscopic rate models to be used in fluid-dynamic codes accounting for the vibrational nonequilibrium. A comparison of analytical fitting of the zero-dimensional data and fluid dynamic global rates has been performed. Nomenclature ci = coefficients for the solution of the master equation Ev = energy of the vth vibrational level k = Boltzmann constant k d = dissociation rate constant k p = rates of the process p

Non-equilibrium plasma kinetics: a state-to-state approach

State-to-state approaches are used to shed light on (a) thermodynamic and transport properties of LTE plasmas, (b) atomic and molecular plasmas for aerospace applications and (c) RF sustained parallel plate reactors. The efforts made by the group of Bari in the kinetics and dynamics of electrons and molecular species are discussed from the point of view of either the master equation approach or the molecular dynamics of elementary processes. Recent experimental results are finally rationalized with a state-to-state kinetics based on the coupling of vibrational kinetics with the Boltzmann equation for the electron energy distribution function.

Coupled solution of a time-dependent collisional-radiative model and Boltzmann equation for atomic hydrogen plasmas: possible implications with LIBS plasmas

Abstract A time-dependent collisional-radiative model coupled to the Boltzmann equation for the electron energy distribution function has been developed for atomic hydrogen plasmas. Different non-equilibrium initial conditions have been studied. The results show that in the early stage of the evolution as well as in the recombination phase, both distribution functions of excited states and of electrons deviate from the corresponding equilibrium (Boltzmann and Maxwell) distributions. The possible implications of the results with LIBS plasmas are finally discussed.

The effect of N+N2 collisions on the non-equilibrium vibrational distributions of nitrogen under reentry conditions

Abstract Global (reactive+non-reactive) quasiclassical state-specific rate coefficients for the vibrational excitation and deexcitation of nitrogen molecules by collision with nitrogen atoms have been used to model a reacting flow. The one-dimensional model used describes the relaxation of N 2 vibrational distributions in the boundary layer surrounding a shuttle reentering the atmosphere. The results single out the strong non-equilibrium character of the vibrational distributions along the coordinate normal to the shuttle surface caused by the dissociation-recombination processes. The results also show the dependence of the vibrational distributions upon inclusion in the model of state-specific N+N 2 ( v ) rates.

Fundamental aspects of plasma chemical physics : Thermodynamics

Classical Thermodynamics.- Two and Three Level Systems.- Statistical Thermodynamics.- Atomic Partition Function.- Molecular Partition Function.- Real Effects: I. Debye-Huckel.- Real Effects: II. Virial Corrections.- Electronic Excitation.- Multi-Temperature Thermodynamics.- Thermodynamics of Planetary Plasmas.- Appendix.

Fundamental aspects of plasma chemical physics

Electron-molecule cross sections and rates involving rotationally, vibrationally and electronically excited states.- Reactivity and relaxation of vibrationally/rotationally excited molecules with open shell atoms.- Formation of vibrationally and rotationally excited molecules during atom recombination on surfaces.- Collisional-radiative models for atomic plasmas.- Collisional-radiative models for molecular plasmas.- Kinetic and Monte Carlo approaches to solve Boltzmann equation for the electron energy distribution functions.- Non-equilibrium plasma kinetics under discharge and post-discharge conditions: coupling problems for low pressure and atmospheric cold plasmas.- Ion transport under strong fields.- PIC (Particle In Cell ) models for low-pressure plasmas.- Negative ion H- for fusion.- Non equilibrium plasma expansion through nozzles.

Recombination-Assisted Nitrogen Dissociation Rates Under Nonequilibrium Conditions

DOI: 10.2514/1.33505 A macroscopic kinetic model accounting for non-Boltzmann vibrational distributions is proposed to describe the dissociation kinetics of a N2=N mixture in a recombination regime. This model is derived by reducing the state-tostate approach to a kinetic equation describing the last vibrational level. The global dissociation rates are related to the last vibrational level population instead of the vibrational temperature. Results obtained by this model were validated with state-to-state calculations. Nomenclature Evib = function to calculate the energy of the vth vibrational state Gv = global gain term for the vth vibrational level G p = gain term for the vth vibrational level due to pth process G � = approximated global gain term for the vth vibrational

The influence of atomic and molecular metastable states in high-enthalpy nozzle expansion nitrogen flows

The role of atomic and molecular electronically excited states on the whole kinetics of an high-enthalpy nozzle flow has been examined by using a self-consistent model which couples Euler equations with appropriate master equations and with the Boltzmann equation for the electron energy distribution function (eedf). The results show that in high-enthalpy flows metastable atomic nitrogen can form structures in the eedf through superelastic collisions, partially smoothed by electron-electron Coulomb collisions.