Vibro-acoustic power flow in plate–fluid layer systems

Attenuation of flexural vibrations by viscous compressible fluid layers is studied by using a power flow analysis. A fluid layer trapped between vibrating surfaces may increase low-frequency damping and cause significant changes in the dynamic behavior of a coupled plate. A prototype system consisting of a clamped plate and a coupled finite air layer is analyzed by using a transfer matrix method. Spectral and spatial distributions of power flow are obtained at different layer thicknesses. Particular attention is given to various dynamic regimes of the fluid layer. Significance of the viscous shear forces and compressibility during the dissipative-to-stiffness transition of the fluid layer are emphasized. At very small layer thicknesses, the increased flow resistance caused by viscous shear forces resulted in local stiffening of the fluid layer which blocked the transmission of the vibrational power. Contributions from three different power flow components, shear, bending and acoustic, are discussed in reference to the dynamic interactions of flexural waves with the fluid layer. The results obtained for different system configurations are briefly reviewed.