Acoustic Wave Propagation at a Fluid-Micropolar Boundary

Abstract

In contrast to a homogeneous isotropic elastic medium with only two elastic constants, a linear elastic micropolar solid is characterized by six independent constants. The solid may consist of particles uniformly distributed in a host matrix. Thus, six different types of wave propagation with four distinct speeds can be found in the dispersion equations. The four distinct speeds are associated with one nondispersively longitudinal displacement wave; one dispersively longitudinal microrotation wave; and two dispersively transverse waves in the presence of couple-stress. In this work, we illustrate the reflected and transmitted fields of an incident acoustic wave propagating at the fluid-micropolar interface. The result is compared to the fluid-isotropic case. It is observed that, due to the mode conversion in the micropolar medium, the micropolar medium should instigate a reducible reflected acoustic wave.