Sound propagation through a rarefied gas. Influence of the gas–surface interaction

Acoustic waves propagating through a rarefied gas between two plates induced by both oscillation and unsteady heating of one of them are considered on the basis of a model of the linearized Boltzmann equation. The gas flow is considered as fully established so that the dependence of all quantities on time is harmonical. The problem is solved for several values of two main parameters determining its solution, namely, the gas rarefaction defined as the ratio of the distance between the plates to the equivalent free path of gaseous molecules, and the oscillation parameter given as the ratio of the intermolecular collision frequency to the wave frequency. The reciprocal relation for such flows is obtained and verified numerically. An influence of the gas–surface accommodation coefficients on the wave characteristics is analyzed by employing the Cercignani–Lampis scattering kernel to the boundary conditions.