Wave propagation characteristics of an infinite fluid-loaded periodic plate

Abstract

A 1-D infinite periodic plate with simple supports placed along equidistant parallel lines is considered using the finite-element method. The plate is loaded with a finite-height fluid column covered on the top with a rigid plate. Results show a relation between the propagation constant of the fluid-loaded structure with its in vacuo counterpart. Since the acoustic medium is an additional wave carrier, the attenuation bands corresponding to the in vacuo structure turn out to be propagating. However, the presence of the fluid can also bring about attenuation regions within the in vacuo propagation bands. Primary propagation constants bring additional waves called space harmonics with them. Hence, a localized coincidence effect is seen where a particular harmonic falls below or above the acoustic wave number, leading to propagation or a mass loading effect. Occasionally, a complete attenuation band is created. This is verified by decomposing the single span displacement profile into the space harmonics and also by computing the frequency response function (FRF) for a finite fluid-loaded periodic plate and observing the huge antiresonance dip in frequency in the exact same frequency band where an attenuation band was predicted for the infinite structure.