Molecular velocity distribution functions in an argon normal shock wave at Mach number 7

Abstract

The streamwise and normal moments of molecular velocity distribution functions throughout an argon normal shock wave have been measured in a Mach number 7.18 wind tunnel flow, and the experimental data have been compared with several analytical and numerical solutions. In the experiments, the molecular population distributions parallel and perpendicular to the direction of flow were derived using a Fabry–Perot etalon to resolve the Doppler shifts in electron-beam-stimulated fluorescence of the gas atoms. Predictions from Monte Carlo techniques give close agreement with the details of the experimental nonequilibrium distribution function contours. Bimodal Maxwellian and ellipsoidal functional forms show only general agreement with overall profile breadth.

Raman spectroscopy of supersonic jets of CO2: Density, condensation, and translational, rotational, and vibrational temperatures

“…In this region the rate of collisions may be considered high enough to maintain the equilibrium T ʈ ϭT Ќ ϭT t between the parallel and perpendicular components of the translational temperature. 7 On the contrary, the relation between rotational and translational temperatures range from nearly equilibrium betweem them, to nonequilibrium, depending markedly on the stagnation conditions of pressure and temperature, and on the points of the zone of silence considered. Finally, vibrational temperature is out of equilibrium with the rotational and translational temperatures from the very beginning of the expansion.…”

“…8 The physical principles, practical difficulties, and limitations for the determination of translational, rotational, and vibrational temperatures under supersonic flow regime have been discussed in connection with the electron impact induced fluorescence ͑EIF͒ technique. 3,[9][10][11] Examples of translational and rotational temperature data from EIF experiments can be found in the literature for a number of specific problems 4,5,7,12 but, for systems where the vibrational degrees of freedom are populated at the temperature of the experiment, data are sparse. On the other hand, establishing the condensation degree of the jet with some accuracy is a difficult problem, particularly in the region not too far downstream from the nozzle.…”

“…Otherwise, T ʈ and T Ќ may be considered in equilibrium. 7 An accurate knowledge of the spatial distribution of translational, rotational, and vibrational temperatures in the jet is essential for the comprehension and quantification of the complex relaxation processes governing the interchange of energy. 8 The physical principles, practical difficulties, and limitations for the determination of translational, rotational, and vibrational temperatures under supersonic flow regime have been discussed in connection with the electron impact induced fluorescence ͑EIF͒ technique.…”

High-Order Discontinuous Galerkin Method for Boltzmann Model Equations

“…The conditions correspond to the experimental measurements of number density and distribution function obtained by Muntz and Holtz. 17 The viscosity coefficient at the reference temperature T . This value of w is based on the detailed comparison of DSMC simulations using the variable-hard-sphere model with experimental measurements.…”

“…17 The distribution function f 1 , however, has to be convolved with the window function of the measurement instrument in order to be compared with the data presented in 17 where details of the convolution procedure can be found. As can be seen from the comparison in Figures 6-7, the BGK and ES models reproduce the experimentally measured distribution function shapes quite well.…”