Study of acoustic wave propagation in micro- and nanochannels

Abstract

The acoustic wave propagating through porous nanomaterials like aerogels, microelectromechanical systems (MEMS) devices, high-frequency acoustic transmission devices or near-vacuum systems, possesses relatively high Knudsen numbers, normally in the transition regime (0.1<Kn<10). In this regime, the characteristic length of micro- and nanochannels is comparable with the mean free path of monatomic gases, in which the classical continuum theory breaks down. In this paper, a theoretical model with the second-order slip boundary is proposed to describe acoustic wave propagation in micro- and nanochannels. The proposed theoretical model provides analytical solutions for the complex wavenumber, attenuation coefficient and other related transmission variables as function of a Knudsen number in the early transition regime (0.1<Kn<1.0), which are valuable for understanding acoustics at micro- and nanoscales. In addition, numerical simulations using the molecular-based direct simulation Monte Carlo (DSMC) method for dilute argon gas are carried out to validate the model and its analytical results. Findings suggest that such a model can effectively predict the acoustic behaviour in micro- and nanochannels.