Control of sound and vibration of fluid-filled cylindrical shells via periodic design and active control

• Design of passive/active periodic shells with fluid loading.
• Band gap formation mechanisms for the periodic shell.
• Suppression of vibration and structure-borne sound.
• Modulation of band gaps via active control strategies.

The wave propagation, vibration transmission and acoustic emission characteristics in the passive and the active periodic shell systems are investigated. A finite element method (FEM) is utilised to conduct the investigation. In the passive periodic shell, two pivotal frequencies (i.e., the cut-off frequency of the periodic shell, and the resonant frequency of flexural vibration of shell ring), which are existed in an arbitrarily high circumferential mode, are found; the frequency range is divided into three regions by these two frequencies. Various band formation mechanisms and the dynamic properties within the three frequency regions are illustrated, with the aid of a series of vibration deformations. Furthermore, an active periodic shell is constructed. Several control methods, such as inverted displacement-, velocity- and acceleration-feedback control strategies, are explored for the active shell. Under these control strategies, the effects of negative stiffness, damping coefficient and mass modulation, can be produced, thus enabling the band gap generable and its characteristics, such as their bandwidth, location and attenuation coefficient, adjustable. The pressure level of the structure-borne sound is also suppressed along the shell within the band gaps.