Conclusion
Based on a direct simulation, comprehensive and systematic studies of the degradation kinetics of a molecular beam at rest made it possible to reveal the qualitative and quantitative relaxation characteristics of the molecular beam to thermal equilibrium with the background gas within the ranges of mass ratios of the injected and background gases 0.1–20 and within velocity ratios of the injection\(0.5 - \sqrt {10} \) for model molecules as hard spheres. The conclusions on the qualitative character of degradation are valid for a wider spectrum of parameters as well. As is established, at an energy of the injected molecules exceeding that of the background gas, during relaxation, a shock effect, i.e., the exceeding of the thermal energy of the injected gas over that of the background gas, is observed. Having been evaluated by analogy with supersonic-flow deceleration, the shock effect is the stronger, the closer the molecules of the injected and background gases in their masses. An initial increase in the energy of the injected molecules that is more considerable for light molecules has been discovered. The dependence of the energy relaxation length on the ratio of the masses and initial velocities of injected molecules has been established.
The data obtained allow us to estimate the dimensions of the region of nonequilibrium mixing of injected and background gases with small values of the intensity of molecular flow in the beam.
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Kutateladze Institute of Thermal Physics, Siberian Division, Russian Academy of Sciences, Novosibirsk 630090. Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 38, No. 4, pp. 103–110, July–August, 1997.
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Morozov, A.A., Plotnikov, M.Y. & Rebrov, A.K. Kinetics of degradation of a molecular beam in a gas at rest. J Appl Mech Tech Phys 38, 590–597 (1997). https://doi.org/10.1007/BF02468106
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DOI: https://doi.org/10.1007/BF02468106