Innovative noise-cancellation strategies for fluid-immersed cylindrical structures using viscous rotational flow and porous functionally graded piezoelectric materials

This article presents a novel acoustic analysis of two coaxial cylindrical shells filled with fluid, explicitly considering the effect of fluid viscosity. This factor is crucial for sound-fluid–structure interactions, particularly in systems that experience detrimental vibrations. The cross-sectional architecture consists of a porous functionally graded piezoelectric (PFGP) coating and two coaxial isotropic cylinders separated by a compressible viscous fluid. The entire structure is completely submerged in a uniform inviscid fluid flow, such as water, and the internal acoustic environment is considered a resonant cavity. A power-law relation is employed to characterize the material properties of the PFGP coating in the thickness direction. The motion of viscous fluid substances is modeled with the three-dimensional (3D) Navier–Stokes equations. The governing equations of motion for each layer of the PFGP coating are derived using an orthotropic laminated model based on the exact linear theory of 3D piezoelasticity. In this regard, the classical state-space technique and the transfer matrix mathematical model are used to solve the problem. Guided wave propagation in elastic isotropic cylinders is adapted to Navier's wave equation, allowing for the inclusion of both longitudinal and torsional waves. Helmholtz decomposition is applied to solve these wave equations. To validate the proposed model, the results are compared with findings from other researchers. Overall, the results indicate that fluids with higher viscosity are more effective in reducing noise levels, and the structure oscillates at a lower speed due to enhanced energy dissipation within the rotational flow layer at the solid–fluid interface.