Sound Propagation in Rarefied Gases

摘要

A study of sound propagation in rarefied gases is described with particular emphasis on the propagation in the geometrical relaxation regime where the sound carrying molecules do not suffer intermolecular collisions during the flight from the transmitter to the receiver. The propagation is characterized by the attenuation and the phase parameters. The dependence of these dispersion parameters on the separation between the transducers, the velocity distribution of the molecules sub sequent to their interaction with the transmitter surface and the boundary conditions describing molecular-surface interactions is ascertained in terms of a semiphenomenological theory. Experiments for measuring the dispersion parameters are described and the results are discussed and compared with theory. A theory and an experiment for determining surface accommodation coefficients using sound propagation in rarefied gas are outlined. Finally a theoretical model is constructed that leads to a reasonable qualitative and quantitative description of sound propagation in rarefied gases. (Author)