The capability of periodic structures to act as filters fortraveling waves is used to control the wave propagation in fluid-loadedshells. Actively controlled actuators are placed periodically along the shellto act as sources of impedance mismatch. Varying the feedback control gain ofthe actuators provides a flexible means for tuning the impedance mismatch andproperly modifying the attenuation characteristics of the shell.A finite-element model, based on the transfer matrix approach, is developedto study the fundamental phenomena governing the coupling between the shell,actuators and the fluid domain surrounding the shell. The geometry of theshell and the fluid domain allows for the formulation of a harmonic-basedmodel with uncoupled circumferential modes. The wave propagation along theshell is studied separately for each mode both for in-vacuum and fluid-loadedshells. The model is used also to predict pass and stop frequency bands fordifferent proportional control gains. The results indicate that the locationand width of the stop bands as well as the attenuation characteristics of theshell can be modified by proper choice of the proportional control gain. Thenumerical predictions demonstrate that the attenuation characteristics can bemaximized within different frequency bands by proper tuning of the actuatorgains.The results obtained demonstrate the feasibility of the concept of activeperiodic shells as an effective means for controlling the width of the stopand pass bands as well as the attenuation characteristics of fluid-loadedshells. Also, the presented analysis provides an invaluable means fordesigning fluid-loaded shells, which are quiet over desired frequency bands.
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