Acoustic radiation and active control from a smart functionally graded submerged hollow cylinder

The 3D piezoelasticity theory and the spatial state-space approach are used to study the steady-state non-axisymmetric sound radiation and scattering characteristics of an infinitely long, arbitrarily thick, orthotropic functionally graded hollow circular cylinder, coupled with an inner (actuator) layer of functionally graded piezoceramic material. The method of stationary phase is employed for evaluation of the radiated far-field pressure integral. Numerical simulations include water-submerged air-filled steel-PZT4 composite cylinders driven by harmonic electromechanical loads or insonified by an obliquely incident plane sound wave. Also, when the actuator layer is operating in the active vibration mode, the effects of the number of control modes on the input voltage required for partial or complete cancellation of the far-field and internal radiated pressures as well as on the backscattering form function and noise reduction amplitudes are examined. Limiting cases are considered and validity of formulation is established by comparison with available data as well as with the aid of a commercial finite element package.