Vibrational Nonequilibrium Effects Research Articles

Monte Carlo trajectory study of Ar + H 2 collisions: Master-equation simulation of a 4500 K shock wave experiment with thermal rotation

Thermally averaged rate coefficients for vibrational state changes and dissociation from individual vibrational levels in H 2-Ar collissions at 4500 K are derived from Monte Carlo quasiclassical trajectory calculations. The rate matrix is completed by linear surprisal interpolation. Relaxation times, induction times, and steady dissociation rates simulating a shock wave experiment are calculated by a matrix-eigenvalue solution of the master equation. Rotational equilibrium is assumed, but vibrational nonequilibrium effects are included in full. The resulting steady dissociation rates are only about 30% less than at equilibrium.

Experiments on radiatively driven harmonic acoustic waves in a confined gas

Measurements are presented of the acoustic pressure resulting from the periodic absorption and emission of radiative energy by an infrared‐active gas contained in a closed, cylindrical tube. The acoustic waves are generated by means of an external, sinusoidally time‐modulated blackbody source. The pressure measurements are for both resonant and nonresonant conditions at acoustic frequencies from about 60 to 600 Hz. Comparison of the measurements with predictions shows that the response is due primarily to the modified‐classical acoustic wave, but that a small contribution from the so‐called radiation‐induced wave can be measured in certain of the tests. Strong effects of vibrational nonequilibrium, similar to those observed previously in spectrophone studies, were found in some of the tests. Generally, the agreement between theory and experiment is satisfactory and provides verification of the basic physical and mathematical models of the theory.

Analysis of an Electric Discharge C02 Mixing Laser

Analysis of an Electric Discharge C02 Mixing Laser

The influence of vibrational nonequilibrium upon infrared radiative energy transfer

The object of this investigation was to study the influence of vibrational nonequilibrium upon infrared radiative energy transfer in nongray, nonisothermal gases. An expression for the radiative flux within a diatomic gas is developed, and the spectroscopic realities of the structure of the fundamental vibration-rotation band are incorporated by expressing the kernel function in terms of the band absorptance. This procedure may readily be extended to include multiple band spectra. Illustrative results showing the effect of vibrational nonequilibrium are given for the case of a gas bounded by two black plates, and within which there is a uniform heat source.

Structure of Radiation-Resisted Shock Waves with Vibrational Nonequilibrium

The continuum equations of gasdynamics are used to study the effect of thermal radiation and vibrational nonequilibrium on the structure of a shock wave. Emphasis is on a description of the gasdynamic phenomena involved rather than on numerical results. For example, a Mollier diagram interpretation, useful for understanding radiation-resisted shock waves, is given. The principal results stem from an analysis of the singular-point structure far upstream and far downstream in the flow. This analysis indicates in a heuristic fashion that a unique solution exists. It also shows that two parameters, a Mach number and the ratio of a radiation length to a relaxation length, primarily govern the qualitative behavior of the flow. Thus, for a specific range of values of these parameters, the vibrational energy overshoots its final equilibrium value. For a different range, a net amount of radiant energy is transferred from the hot gas behind the adiabatic shock to the gas far downstream.