Acoustics and stability of fluid flow in a periodic elastic structure

A fluid Bows horizontally through a fluid-structure system comprising alternating elastic solid and liquid constituents arranged periodically in the vertical direction. An exact analysis is performed to consider the existence and stability of small acoustic waves and disturbances. The presence of the flow introduces the possibility of flow-induced Butter. Unstable waves are generally possible for M of order unity, M being the Mach number relative to the speed of shear waves in the solid. Instabilities can appear for much lower values for antisymmetric flexural type motion. In that case it is found that a critical wavenumber exists, indicating that the layered system is inherently unstable to long wavelength disturbances. (C) 1997 Academic Press Limited.