Active/passive control of sound radiation and power flow in fluid-loaded shells

Sound radiation and power flow of fluid-loaded shells are controlled using multiple stiffening rings treated with active/passive treatments. A finite element model is developed to study the fundamental phenomena governing the coupling between the shell, active/passive treatments and the fluid domain surrounding the shell. The geometry of the shell and the fluid domain allo ws the formulation of a harmonic-based model with uncoupled circumferential modes. The finite element model is used to predict the structural and acou stical behavior of the shell when both passive and active control technique s are applied to the stiffening rings. The numerical results obtained indic ate that the active/passive hybrid treatment can significantly reduce the a mplitude of vibration and the sound radiation into the fluid domain without substantially increasing the mass of the shell. The active/passive rings a re found to be particularly effective in controlling the higher order lobar modes. The presented finite element model along with the power flow analys is provides an invaluable means for the design of quiet fluid-loaded shells , (C) 2000 Elsevier Science Ltd, All rights reserved.